build(lint): extend ESLint to .ts/.tsx via typescript-eslint

As files convert to TypeScript they must keep the react-hooks enforcement.
Added a .ts/.tsx config block using the typescript-eslint parser with the same
rules-of-hooks/exhaustive-deps/react-refresh rules; swapped core no-undef +
no-unused-vars (type-blind) for TS-aware equivalents. Verified 'npm run lint'
traverses .ts and flags issues there; 0 errors on the existing .ts files.

Co-Authored-By: Claude Opus 4.8 <noreply@anthropic.com>

eslint.config.mjs

@@ -2,6 +2,7 @@ import js from '@eslint/js';
 import globals from 'globals';
 import reactHooks from 'eslint-plugin-react-hooks';
 import reactRefresh from 'eslint-plugin-react-refresh';
+import tseslint from 'typescript-eslint';
 
 // Flat config scoped to the React client. The point is enforcement of the two
 // rules that catch real React bugs — rules-of-hooks (conditional hooks) and
@@ -33,4 +34,33 @@ export default [
       'no-empty': ['warn', { allowEmptyCatch: true }],
     },
   },
+  {
+    // TypeScript files: same react-hooks/react-refresh enforcement, via the
+    // TS parser. TS itself handles undefined identifiers + unused vars, so the
+    // core rules that don't understand types are swapped for their TS-aware
+    // equivalents. (Not the full typescript-eslint recommended set — this keeps
+    // the signal focused on the same correctness rules as the JS config.)
+    files: ['client/**/*.{ts,tsx}'],
+    languageOptions: {
+      parser: tseslint.parser,
+      ecmaVersion: 2023,
+      sourceType: 'module',
+      globals: { ...globals.browser },
+      parserOptions: { ecmaFeatures: { jsx: true } },
+    },
+    plugins: {
+      'react-hooks': reactHooks,
+      'react-refresh': reactRefresh,
+      '@typescript-eslint': tseslint.plugin,
+    },
+    rules: {
+      'react-hooks/rules-of-hooks': 'error',
+      'react-hooks/exhaustive-deps': 'warn',
+      'react-refresh/only-export-components': ['warn', { allowConstantExport: true }],
+      'no-undef': 'off', // TypeScript checks this
+      'no-unused-vars': 'off',
+      '@typescript-eslint/no-unused-vars': ['warn', { varsIgnorePattern: '^[A-Z_]', argsIgnorePattern: '^_' }],
+      'no-empty': ['warn', { allowEmptyCatch: true }],
+    },
+  },
 ];

package-lock.json

@@ -68,6 +68,7 @@
         "postcss": "^8.4.47",
         "tailwindcss": "^3.4.14",
         "typescript": "^6.0.3",
+        "typescript-eslint": "^8.62.1",
         "vite": "^5.4.10",
         "vite-plugin-pwa": "^1.3.0",
         "vitest": "^4.1.8"
@@ -6063,6 +6064,262 @@
       "dev": true,
       "license": "MIT"
     },
+    "node_modules/@typescript-eslint/eslint-plugin": {
+      "version": "8.62.1",
+      "resolved": "https://registry.npmjs.org/@typescript-eslint/eslint-plugin/-/eslint-plugin-8.62.1.tgz",
+      "integrity": "sha512-4EQM77WgVNxj7OkL/5b/D/xZsw00G577+UriYTC7JF5opcF3T2AuoeY7ueLaZgSVjSgCS6yOAJB5bRGLPSJUzA==",
+      "dev": true,
+      "license": "MIT",
+      "dependencies": {
+        "@eslint-community/regexpp": "^4.12.2",
+        "@typescript-eslint/scope-manager": "8.62.1",
+        "@typescript-eslint/type-utils": "8.62.1",
+        "@typescript-eslint/utils": "8.62.1",
+        "@typescript-eslint/visitor-keys": "8.62.1",
+        "ignore": "^7.0.5",
+        "natural-compare": "^1.4.0",
+        "ts-api-utils": "^2.5.0"
+      },
+      "engines": {
+        "node": "^18.18.0 || ^20.9.0 || >=21.1.0"
+      },
+      "funding": {
+        "type": "opencollective",
+        "url": "https://opencollective.com/typescript-eslint"
+      },
+      "peerDependencies": {
+        "@typescript-eslint/parser": "^8.62.1",
+        "eslint": "^8.57.0 || ^9.0.0 || ^10.0.0",
+        "typescript": ">=4.8.4 <6.1.0"
+      }
+    },
+    "node_modules/@typescript-eslint/eslint-plugin/node_modules/ignore": {
+      "version": "7.0.5",
+      "resolved": "https://registry.npmjs.org/ignore/-/ignore-7.0.5.tgz",
+      "integrity": "sha512-Hs59xBNfUIunMFgWAbGX5cq6893IbWg4KnrjbYwX3tx0ztorVgTDA6B2sxf8ejHJ4wz8BqGUMYlnzNBer5NvGg==",
+      "dev": true,
+      "license": "MIT",
+      "engines": {
+        "node": ">= 4"
+      }
+    },
+    "node_modules/@typescript-eslint/parser": {
+      "version": "8.62.1",
+      "resolved": "https://registry.npmjs.org/@typescript-eslint/parser/-/parser-8.62.1.tgz",
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+      "license": "MIT",
+      "dependencies": {
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+        "@typescript-eslint/types": "8.62.1",
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+        "@typescript-eslint/visitor-keys": "8.62.1",
+        "debug": "^4.4.3"
+      },
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+      },
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+        "typescript": ">=4.8.4 <6.1.0"
+      }
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+        "minimatch": "^10.2.2",
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+      },
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+        "typescript": ">=4.8.4 <6.1.0"
+      }
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+      "resolved": "https://registry.npmjs.org/@typescript-eslint/visitor-keys/-/visitor-keys-8.62.1.tgz",
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+      "dev": true,
+      "license": "MIT",
+      "dependencies": {
+        "@typescript-eslint/types": "8.62.1",
+        "eslint-visitor-keys": "^5.0.0"
+      },
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+      },
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+        "url": "https://opencollective.com/typescript-eslint"
+      }
+    },
+    "node_modules/@typescript-eslint/visitor-keys/node_modules/eslint-visitor-keys": {
+      "version": "5.0.1",
+      "resolved": "https://registry.npmjs.org/eslint-visitor-keys/-/eslint-visitor-keys-5.0.1.tgz",
+      "integrity": "sha512-tD40eHxA35h0PEIZNeIjkHoDR4YjjJp34biM0mDvplBe//mB+IHCqHDGV7pxF+7MklTvighcCPPZC7ynWyjdTA==",
+      "dev": true,
+      "license": "Apache-2.0",
+      "engines": {
+        "node": "^20.19.0 || ^22.13.0 || >=24"
+      },
+      "funding": {
+        "url": "https://opencollective.com/eslint"
+      }
+    },
     "node_modules/@vitejs/plugin-react": {
       "version": "4.7.0",
       "resolved": "https://registry.npmjs.org/@vitejs/plugin-react/-/plugin-react-4.7.0.tgz",
@@ -12840,6 +13097,19 @@
         "tree-kill": "cli.js"
       }
     },
+    "node_modules/ts-api-utils": {
+      "version": "2.5.0",
+      "resolved": "https://registry.npmjs.org/ts-api-utils/-/ts-api-utils-2.5.0.tgz",
+      "integrity": "sha512-OJ/ibxhPlqrMM0UiNHJ/0CKQkoKF243/AEmplt3qpRgkW8VG7IfOS41h7V8TjITqdByHzrjcS/2si+y4lIh8NA==",
+      "dev": true,
+      "license": "MIT",
+      "engines": {
+        "node": ">=18.12"
+      },
+      "peerDependencies": {
+        "typescript": ">=4.8.4"
+      }
+    },
     "node_modules/ts-interface-checker": {
       "version": "0.1.13",
       "resolved": "https://registry.npmjs.org/ts-interface-checker/-/ts-interface-checker-0.1.13.tgz",
@@ -13013,6 +13283,30 @@
         "node": ">=14.17"
       }
     },
+    "node_modules/typescript-eslint": {
+      "version": "8.62.1",
+      "resolved": "https://registry.npmjs.org/typescript-eslint/-/typescript-eslint-8.62.1.tgz",
+      "integrity": "sha512-vymnnM5g0AKQDSAyfP12nMIBvgwgA42syg74kkuZ4x1VuTzwQKwc5h9rGxeShCjny5o+zWAb6OEoz7XLgrIkIw==",
+      "dev": true,
+      "license": "MIT",
+      "dependencies": {
+        "@typescript-eslint/eslint-plugin": "8.62.1",
+        "@typescript-eslint/parser": "8.62.1",
+        "@typescript-eslint/typescript-estree": "8.62.1",
+        "@typescript-eslint/utils": "8.62.1"
+      },
+      "engines": {
+        "node": "^18.18.0 || ^20.9.0 || >=21.1.0"
+      },
+      "funding": {
+        "type": "opencollective",
+        "url": "https://opencollective.com/typescript-eslint"
+      },
+      "peerDependencies": {
+        "eslint": "^8.57.0 || ^9.0.0 || ^10.0.0",
+        "typescript": ">=4.8.4 <6.1.0"
+      }
+    },
     "node_modules/unbox-primitive": {
       "version": "1.1.0",
       "resolved": "https://registry.npmjs.org/unbox-primitive/-/unbox-primitive-1.1.0.tgz",

package.json

@@ -83,6 +83,7 @@
     "postcss": "^8.4.47",
     "tailwindcss": "^3.4.14",
     "typescript": "^6.0.3",
+    "typescript-eslint": "^8.62.1",
     "vite": "^5.4.10",
     "vite-plugin-pwa": "^1.3.0",
     "vitest": "^4.1.8"