The pack library was a navigation dead end: it is not a bottom-nav tab and it
draws no header of its own, and it was missing from shellBackRoutes — so the
shell rendered neither an app bar nor a bottom bar. Once there, the system Back
gesture was the only way off the screen.
It is reached by drilling in from four places (Home "All packs", the Play hub,
the question composer's empty state, and the weekly recap), so it needs the same
shell back affordance its own detail page (QUESTION_CATEGORY) already had.
Audited the whole route table for the same hole rather than patching just this
one. Every other non-tab route either sits in shellBackRoutes or draws its own
back; the two remaining are PAIR_PROMPT and RECOVERY, which are self-contained
entry flows with their own CTAs, so they are intentionally left alone.
Verified live on both fixtures: Home -> Question Packs -> a pack -> back ->
Question Packs -> back -> Home, in dark and light. Unit tests green, 0 FATAL.
Co-Authored-By: Claude Opus 4.8 <noreply@anthropic.com>
089437e415