Prevent Android chats from freezing or going blank (#1989)

* fix(app): stabilize streamed chat rendering

Use deterministic Markdown AST keys and preserve unique row identities when an assistant message resumes after a tool. Keep native gesture and plan-card children correctly keyed to avoid unsupported Fabric reconciliation paths.

* fix(app): stabilize retained native panels

Keep retained workspace roots in a stable native order and make active
panels present in the selection commit. Hidden panels now stop expensive
subscriptions and animations without losing mounted state.

* fix(app): harden retained panel activity

docs/coding-standards.md

@@ -84,6 +84,10 @@ For testing rules, see [testing.md](testing.md).
 - Components render and dispatch — they don't compute transitions. Two-plus interacting `useState`s → extract a reducer.
 - Never define components inside other components. Module-scope only.
 - Subscribe narrowly: select primitives from stores, pass `status` not `agent`, use `useShallow` / deep-equal when returning derived arrays/objects.
+- Collection rows do not independently subscribe to a high-frequency global store. The collection owner selects structurally shared indexes once, derives a keyed row model with `useMemo`, and passes entries to rows. This keeps retained hidden collections current without running one selector per row on every store update.
+- Equality functions prevent React renders; they do not prevent selector callbacks from running. A selector attached to a hot store must be O(1) when its relevant source references have not changed.
+- Retained native panels use `RetainedPanel`. If an existing gesture/layout wrapper must own visibility, wrap its contents in `RetainedPanelActivity` instead. Keep keyed panel roots in a stable sibling order, include the newly active panel in the same render, centralize subscriptions, and gate genuine effects through `useRetainedPanelActive`. Do not use `Suspense` or render freezing for this on native: those techniques change native tree ownership instead of merely stopping work.
+- Infinite animations are subscriptions. Start them only while their retained panel is active, and cancel a shared clock when its final active consumer leaves. Match scheduler cadence to the actual visual cadence; do not run a 60 fps interpolation when the rendered value changes only a few times per second.
 - Stable references for props that cross `memo` boundaries or feed dependency arrays. Static literals at module scope `as const`; derived with `useMemo`; handlers with `useCallback` only when there's a memoized beneficiary.
 - Use stable ids for `key`, never array index for reorderable/filterable lists.
 - Context for stable values (theme, auth). Store with selectors for state that changes.