docs: refine porting rule — exact on behavior+feel, idiomatic on implementation

Operator guidance: parity is about the user experience (layout, copy,
states, and especially responsiveness — caching exists to make the UI
feel instant), not literal transliteration of Flutter's Dart. Replicate
the behavior faithfully but reach it with the best well-supported native
mechanism (Room+Flow, Compose, WorkManager, Media3) rather than copying
drift watch() / Riverpod invalidate. A more native approach that improves
the UX is preferred — recorded as an intentional divergence in the parity
map.

Co-Authored-By: Claude Opus 4.7 (1M context) <noreply@anthropic.com>

CLAUDE.md

@@ -13,10 +13,17 @@ exists in Flutter:
    opened the Flutter file in this session, you have not earned the right to
    write the Android version.
 
-2. **Replicate it exactly.** Match the behavior, the layout structure, the
-   section order, the empty/loading/error states, the copy strings, the data
-   sources, and the edge cases. Same number of rows, same fields per row, same
-   tap targets.
+2. **Replicate the user-visible behavior exactly; implement it idiomatically.**
+   Match what the user sees and feels: layout structure, section order, empty/
+   loading/error states, copy strings, edge cases, and — critically — the
+   **responsiveness** (the app caches to make the UI feel instant; preserve
+   that). But you do NOT have to copy Flutter's *implementation*. Flutter uses
+   drift `watch()` + Riverpod `invalidate`; the well-supported Android idioms
+   are Room + Flow, Compose state, WorkManager, Media3. **Prefer the native
+   mechanism that delivers the same or better UX** over a literal transliteration
+   of the Dart. Exact on behavior + feel; idiomatic on structure. If a more
+   native approach genuinely improves the experience, do that (and note it in
+   the parity map as an intentional, better-supported divergence).
 
 3. **Never silently substitute a different design.** If the faithful port seems
    hard, blocked, or impossible, STOP and verify by reading more of the Flutter