feat: the designed Settings screen, structured as §36 specifies

closes #33

Settings is now a root with §36's sections rather than one screen of notification
toggles that called itself a working surface. Reminders move underneath it as a
child destination; the banner is gone because the claim it made stopped being
true, not because the screen changed.

A ROW FOR AN UNBUILT FEATURE IS ABSENT, NOT DISABLED

§36 lists six sections and this shows the two that have something behind them.
A greyed-out "Export My Data" is a promise with no delivery date, and a disabled
"Delete My Data" tells a user that control over their own health data exists and
that they may not have it. In a product whose whole argument is that the data is
theirs, that is a bad first thing to say. Privacy & Security arrives with #34 to
#37, Appearance with Batch 08, Premium with Batch 07.

ONE COPY OF THE FERTILITY DISCLAIMER

About needs it, and it was already a literal in TodayScreen and CalendarScreen —
a third copy would have made two versions of a safety promise inevitable. Now a
string resource all three read. Notifications still deliberately omit it: a long
sentence about fertility on a lock screen is the leak the discreet copy exists
to prevent.

The version is read from PackageManager rather than BuildConfig, so it reports
what is actually installed — the number a person reads out when something is
wrong.

A DOC TRIGGER THAT COULD NOT FIRE

docs/design/README.md's trigger is "any new user-facing screen or state" while
its Governs listed only docs/design/** and core/designsystem/**, so adding a
screen fired nothing. Same class of defect as the architecture doc's, found the
same way — by adding the thing the trigger is about and watching it not fire.
Widened, and verified by running doc-triggers.py against the new file.

Driven on PeriodMinSdk26: the root renders, rows expand in place, reminders open
as a child, and back returns to the root rather than exiting.

Co-Authored-By: Claude Opus 5 (1M context) <noreply@anthropic.com>

app/src/main/kotlin/dev/privacyllc/period/feature/calendar/CalendarScreen.kt

@@ -40,11 +40,13 @@ import androidx.compose.ui.graphics.Color
 import androidx.compose.ui.semantics.clearAndSetSemantics
 import androidx.compose.ui.semantics.contentDescription
 import androidx.compose.ui.text.font.FontWeight
+import androidx.compose.ui.res.stringResource
 import androidx.compose.ui.text.style.TextAlign
 import androidx.compose.ui.tooling.preview.Preview
 import androidx.compose.ui.unit.dp
 import androidx.hilt.navigation.compose.hiltViewModel
 import androidx.lifecycle.compose.collectAsStateWithLifecycle
+import dev.privacyllc.period.R
 import dev.privacyllc.period.designsystem.PeriodTheme
 import dev.privacyllc.period.designsystem.PeriodThemeDefaults
 import dev.privacyllc.period.designsystem.art.ConfirmedPeriodMarker
@@ -301,8 +303,7 @@ private fun Legend() {
     }
     Spacer(Modifier.height(8.dp))
     Text(
-        "Fertility and ovulation dates are estimates based on cycle history and are not " +
+        stringResource(R.string.fertility_disclaimer),
-            "intended to be used as contraception or as a medical diagnosis.",
         style = MaterialTheme.typography.bodySmall,
         color = MaterialTheme.colorScheme.onSurfaceVariant,
     )

app/src/main/kotlin/dev/privacyllc/period/feature/settings/NotificationSettingsScreen.kt

@@ -41,9 +41,10 @@ import java.time.format.DateTimeFormatter
 /**
  * Notification settings — §28's privacy mode and §29's six toggles.
  *
- * The designed Settings screen is Batch 06; this is the working surface for the
+ * A child of [SettingsScreen] rather than the Settings tab itself. It carried a
- * plumbing, and it says so at the top for the same reason the Batch 01 Today
+ * "Batch 05 · working surface" banner until the §36 tree existed to hold it;
- * screen did: a convincing mock is how a screen comes to be believed finished.
+ * the banner is gone because the claim it made is no longer true, not because
+ * the screen changed.
  */
 @Composable
 fun NotificationSettingsScreen(viewModel: NotificationSettingsViewModel = hiltViewModel()) {
@@ -79,13 +80,6 @@ private fun NotificationSettingsContent(
             .verticalScroll(rememberScrollState())
             .padding(16.dp),
     ) {
-        Text(
-            "Batch 05 · working surface — the designed Settings screen is Batch 06",
-            style = MaterialTheme.typography.labelSmall,
-            color = MaterialTheme.colorScheme.onSurfaceVariant,
-        )
-        Spacer(Modifier.height(16.dp))
-
         Text("How reminders appear", style = MaterialTheme.typography.titleMedium)
         Spacer(Modifier.height(4.dp))
         Text(

app/src/main/kotlin/dev/privacyllc/period/feature/settings/SettingsScreen.kt

@@ -0,0 +1,199 @@
+package dev.privacyllc.period.feature.settings
+
+import androidx.compose.animation.AnimatedVisibility
+import androidx.compose.foundation.clickable
+import androidx.compose.foundation.layout.Arrangement
+import androidx.compose.foundation.layout.Column
+import androidx.compose.foundation.layout.Row
+import androidx.compose.foundation.layout.Spacer
+import androidx.compose.foundation.layout.fillMaxSize
+import androidx.compose.foundation.layout.fillMaxWidth
+import androidx.compose.foundation.layout.height
+import androidx.compose.foundation.layout.padding
+import androidx.compose.foundation.rememberScrollState
+import androidx.compose.foundation.verticalScroll
+import androidx.compose.material3.HorizontalDivider
+import androidx.compose.material3.MaterialTheme
+import androidx.compose.material3.Text
+import androidx.compose.runtime.Composable
+import androidx.compose.runtime.getValue
+import androidx.compose.runtime.mutableStateOf
+import androidx.compose.runtime.remember
+import androidx.compose.runtime.setValue
+import androidx.compose.ui.Alignment
+import androidx.compose.ui.Modifier
+import androidx.compose.ui.platform.LocalContext
+import androidx.compose.ui.res.stringResource
+import androidx.compose.ui.tooling.preview.Preview
+import androidx.compose.ui.unit.dp
+import dev.privacyllc.period.R
+import dev.privacyllc.period.designsystem.PeriodTheme
+
+/**
+ * Settings, structured as PRODUCT_PLAN.md §36 specifies.
+ *
+ * ## Why sections appear as they are built
+ *
+ * §36 describes the whole tree — Cycle, Notifications, Privacy & Security,
+ * Appearance, Premium, About. This screen shows only the sections that have
+ * something behind them, and **a row for an unbuilt feature is absent rather
+ * than disabled**.
+ *
+ * That is deliberate. A greyed-out "Export My Data" is a promise with no
+ * delivery date, and in a privacy app specifically it is worse than silence: a
+ * user who sees a disabled Delete My Data has been told the feature exists and
+ * that they may not have it. A section that is not there yet is simply not
+ * there yet, and the tracker is where the plan lives.
+ *
+ * So Privacy & Security arrives with #34 to #37, Appearance with Batch 08's
+ * theme control, and Premium with Batch 07.
+ */
+@Composable
+fun SettingsScreen(onOpenNotifications: () -> Unit) {
+    Column(
+        Modifier
+            .fillMaxSize()
+            .verticalScroll(rememberScrollState())
+            .padding(horizontal = 16.dp, vertical = 8.dp),
+    ) {
+        SectionHeader("Notifications")
+        SettingsRow(
+            title = "Reminders and privacy",
+            subtitle = "What a reminder says, and what it withholds",
+            onClick = onOpenNotifications,
+        )
+
+        Spacer(Modifier.height(8.dp))
+        SectionHeader("About")
+        ExpandableRow(
+            title = "How predictions work",
+            body = "The app learns from the period dates you confirm. It weighs your " +
+                "recent cycles more heavily than old ones, and it measures how much " +
+                "they vary — that variation is what sets the window and the confidence " +
+                "label, so a steady cycle gets a tight window and an irregular one " +
+                "gets an honest wide one.\n\n" +
+                "It never presents a bare date as fact, and until there is enough of " +
+                "your own history it says so rather than falling back on a generic " +
+                "28-day cycle.",
+        )
+        ExpandableRow(
+            title = "Fertility disclaimer",
+            body = stringResource(R.string.fertility_disclaimer),
+        )
+        StaticRow(title = "Version", value = versionName())
+    }
+}
+
+/**
+ * The installed version, read from the package manager rather than a
+ * `BuildConfig` constant — so it reports what is actually on the device, which
+ * is the number a person reads out when something is wrong.
+ */
+@Composable
+private fun versionName(): String {
+    val context = LocalContext.current
+    return remember(context) {
+        runCatching {
+            context.packageManager.getPackageInfo(context.packageName, 0).versionName
+        }.getOrNull() ?: "unknown"
+    }
+}
+
+@Composable
+private fun SectionHeader(text: String) {
+    Spacer(Modifier.height(16.dp))
+    Text(
+        text,
+        style = MaterialTheme.typography.titleSmall,
+        color = MaterialTheme.colorScheme.primary,
+    )
+    Spacer(Modifier.height(4.dp))
+}
+
+@Composable
+private fun SettingsRow(title: String, subtitle: String, onClick: () -> Unit) {
+    Column(
+        Modifier
+            .fillMaxWidth()
+            .clickable(onClick = onClick)
+            .padding(vertical = 12.dp),
+    ) {
+        Text(title, style = MaterialTheme.typography.bodyLarge)
+        Text(
+            subtitle,
+            style = MaterialTheme.typography.bodySmall,
+            color = MaterialTheme.colorScheme.onSurfaceVariant,
+        )
+    }
+    HorizontalDivider()
+}
+
+/**
+ * A row that opens its own explanation.
+ *
+ * Expanding in place rather than navigating: every one of these is a paragraph,
+ * and a destination that holds one paragraph is a back-stack entry the user has
+ * to spend to read two sentences.
+ */
+@Composable
+private fun ExpandableRow(title: String, body: String) {
+    var open by remember { mutableStateOf(false) }
+    Column(
+        Modifier
+            .fillMaxWidth()
+            .clickable { open = !open }
+            .padding(vertical = 12.dp),
+    ) {
+        Row(
+            Modifier.fillMaxWidth(),
+            horizontalArrangement = Arrangement.SpaceBetween,
+            verticalAlignment = Alignment.CenterVertically,
+        ) {
+            Text(title, style = MaterialTheme.typography.bodyLarge)
+            // Text rather than a chevron: it states the action, and TalkBack
+            // reads it without needing a content description nobody wrote.
+            Text(
+                if (open) "Hide" else "Show",
+                style = MaterialTheme.typography.labelMedium,
+                color = MaterialTheme.colorScheme.primary,
+            )
+        }
+        AnimatedVisibility(open) {
+            Text(
+                body,
+                style = MaterialTheme.typography.bodySmall,
+                color = MaterialTheme.colorScheme.onSurfaceVariant,
+                modifier = Modifier.padding(top = 8.dp),
+            )
+        }
+    }
+    HorizontalDivider()
+}
+
+@Composable
+private fun StaticRow(title: String, value: String) {
+    Row(
+        Modifier
+            .fillMaxWidth()
+            .padding(vertical = 12.dp),
+        horizontalArrangement = Arrangement.SpaceBetween,
+    ) {
+        Text(title, style = MaterialTheme.typography.bodyLarge)
+        Text(
+            value,
+            style = MaterialTheme.typography.bodyLarge,
+            color = MaterialTheme.colorScheme.onSurfaceVariant,
+        )
+    }
+}
+
+@Preview(name = "Settings · light", showBackground = true)
+@Preview(
+    name = "Settings · dark",
+    showBackground = true,
+    uiMode = android.content.res.Configuration.UI_MODE_NIGHT_YES,
+)
+@Composable
+private fun PreviewSettingsRoot() = PeriodTheme {
+    SettingsScreen(onOpenNotifications = {})
+}

app/src/main/kotlin/dev/privacyllc/period/feature/today/TodayScreen.kt

@@ -34,11 +34,13 @@ import androidx.compose.ui.Alignment
 import androidx.compose.ui.Modifier
 import androidx.compose.ui.semantics.clearAndSetSemantics
 import androidx.compose.ui.semantics.contentDescription
+import androidx.compose.ui.res.stringResource
 import androidx.compose.ui.text.style.TextAlign
 import androidx.compose.ui.tooling.preview.Preview
 import androidx.compose.ui.unit.dp
 import androidx.hilt.navigation.compose.hiltViewModel
 import androidx.lifecycle.compose.collectAsStateWithLifecycle
+import dev.privacyllc.period.R
 import dev.privacyllc.period.designsystem.PeriodTheme
 import dev.privacyllc.period.designsystem.PeriodThemeDefaults
 import dev.privacyllc.period.designsystem.art.CycleProgressMark
@@ -284,8 +286,7 @@ private fun FertilitySection(estimate: FertilityEstimate?, likelihood: Fertility
 @Composable
 private fun FertilityDisclaimer() {
     Text(
-        "Fertility and ovulation dates are estimates based on cycle history and are not " +
+        stringResource(R.string.fertility_disclaimer),
-            "intended to be used as contraception or as a medical diagnosis.",
         style = MaterialTheme.typography.bodySmall,
         color = MaterialTheme.colorScheme.onSurfaceVariant,
         textAlign = TextAlign.Center,

app/src/main/kotlin/dev/privacyllc/period/navigation/PeriodApp.kt

@@ -40,6 +40,7 @@ import dev.privacyllc.period.feature.calendar.CalendarScreen
 import dev.privacyllc.period.feature.insights.InsightsScreen
 import dev.privacyllc.period.feature.onboarding.OnboardingScreen
 import dev.privacyllc.period.feature.settings.NotificationSettingsScreen
+import dev.privacyllc.period.feature.settings.SettingsScreen
 import dev.privacyllc.period.feature.today.TodayScreen
 
 /**
@@ -137,10 +138,17 @@ fun PeriodApp() {
             composable(PeriodDestination.CALENDAR.route) { CalendarScreen() }
             composable(PeriodDestination.INSIGHTS.route) { InsightsScreen() }
 
-            // Settings shows the notification plumbing from Batch 05. The
+            // Settings is a root with children, so the tab lands on the §36
-            // designed screen — cycle, privacy and security, appearance,
+            // tree and reminders live one level down. The tab item's own
-            // premium, about — is Batch 06, and this surface says so on itself.
+            // navigate() pops back to this start destination, which is what
-            composable(PeriodDestination.SETTINGS.route) { NotificationSettingsScreen() }
+            // makes tapping Settings from inside reminders return here rather
+            // than doing nothing.
+            composable(PeriodDestination.SETTINGS.route) {
+                SettingsScreen(
+                    onOpenNotifications = { navController.navigate(SETTINGS_NOTIFICATIONS) },
+                )
+            }
+            composable(SETTINGS_NOTIFICATIONS) { NotificationSettingsScreen() }
         }
     }
 }
@@ -181,3 +189,6 @@ private fun PlaceholderScreen(title: String) {
 private fun PlaceholderPreview() {
     PeriodTheme { PlaceholderScreen("Calendar") }
 }
+
+/** Reminder settings, a child of the Settings tab rather than a fifth tab. */
+private const val SETTINGS_NOTIFICATIONS = "settings/notifications"

app/src/main/res/values/strings.xml

@@ -17,4 +17,17 @@
     <string name="tab_calendar">Calendar</string>
     <string name="tab_insights">Insights</string>
     <string name="tab_settings">Settings</string>
+
+    <!--
+      One copy, read by every surface that shows a fertility estimate.
+
+      §18 scopes this line to "near fertility features and in About", and it was
+      a literal in two screens before Settings needed a third. Two copies of a
+      safety disclaimer is how two versions of a promise come to exist — the
+      failure DOC_TRUST_MAP.md exists to prevent, in code rather than prose.
+
+      Notifications deliberately do NOT carry it: a long sentence about
+      fertility on a lock screen is the leak the discreet copy exists to avoid.
+    -->
+    <string name="fertility_disclaimer">Fertility and ovulation dates are estimates based on cycle history and are not intended to be used as contraception or as a medical diagnosis.</string>
 </resources>

docs/design/README.md

@@ -4,8 +4,9 @@
 Status: Current
 Owner: _null
 Last reviewed: 2026-08-18
-Governs: docs/design/**, core/designsystem/** — the design tokens — and the
+Governs: docs/design/**, core/designsystem/**, app/src/main/kotlin/**,
-         product's tone and interface copy
+         app/src/main/res/values/** — the design tokens, every user-facing
+         screen, and the product's tone and interface copy
 Review trigger: Any new user-facing screen or state; any change to the colour or
                 type tokens; any change to notification copy or to a privacy or
                 fertility disclaimer
@@ -125,6 +126,23 @@ and it puts the failure in front of whoever is editing. And the `Surface` lives
 in the theme rather than in each screen, so a screen without a `Scaffold` cannot
 forget it.
 
+## A row for an unbuilt feature is absent, not disabled
+
+Settings is built as `PRODUCT_PLAN.md` §36 structures it, and it shows only the
+sections that have something behind them. Privacy & Security arrives with the
+issues that fill it; Appearance and Premium with their batches.
+
+The alternative — every §36 row present and greyed out — is worse here than in
+most apps. A disabled *Export My Data* is a promise with no delivery date, and a
+disabled *Delete My Data* tells a user that the control over their own health
+data exists and that they may not have it. In a product whose entire argument is
+that the data is theirs, that is a bad first thing to say.
+
+Absent is honest, and the tracker is where the plan lives — which is the same
+rule [`../data/README.md`](../data/README.md) applies to placeholder images, for
+the same reason: something that looks finished outlives the issue that would
+have replaced it.
+
 ## The states most often left undesigned
 
 Designed here on purpose, because they are the two most people meet first: