Smooth mobile keyboard transitions (#4275)

* perf(app): smooth mobile keyboard transitions

Animating dock padding forced Fabric and Yoga to relayout the chat tree on every keyboard frame, producing visible stepping and React list churn. Keep the surface full-height and move it as one translated unit, with scroll range and portal measurements updated only after keyboard motion settles.\n\niOS keeps its native keyboard animation driver behind the same component boundary because its Reanimated signal reports the endpoint at animation start.

* fix(app): isolate native keyboard implementation

docs/floating-panels.md

@@ -134,19 +134,39 @@ The fix for transforms is Gotcha 3. The fix for context is Gotcha 7.
 
 ## Gotcha 3 — Keyboard layout and portal anchors
 
-Move the chat surface with worklet-driven bottom padding from
-`KeyboardShiftProvider`. Padding keeps the stream, composer, visual position,
-and native hit testing in the same layout. Do not translate the stream and
-composer independently.
+`KeyboardTranslateView` owns visual keyboard motion. Android uses the
+controller's Reanimated signal. iOS uses its native-driver `Animated.event`
+signal because the stock iOS Reanimated value changes at move start, while
+writing a replacement Reanimated value every frame interrupts UIKit's hide
+animation. Keep this platform choice inside `KeyboardTranslateView`.
 
-Do not use the controller's raw keyboard progress for the padding. It can retain
-a nonzero value after the keyboard closes. The shared provider normalizes that
-state and reconciles native animation-end events.
+`KeyboardDock` always keeps the chat surface at full height and wraps it in
+`KeyboardTranslateView`. The panel root clips it at the header edge, so rows
+slide under the header on open and out from under it on close. Do not swap the
+dock to keyboard padding at rest. Changing its height creates either a blank
+band or a paused transition when the inverted list updates its viewport.
 
-`measureInWindow` already includes the dock's current padding layout. When a
-portal opens, snapshot the current shift and apply only the subsequent shift
-delta to its animated `bottom`. Adding the full shift moves the portal twice and
-can place it over the composer controls.
+Do not animate a layout prop through the keyboard transition. On Android
+Fabric, each animated layout update clones the shadow tree and runs Yoga over
+the dock subtree. This measured about 10 ms per frame on the emulator and the
+mounted layouts arrived in bursts every 2–4 frames. A transform does not dirty
+layout. Preserve the translated dock's history scroll range with a far-end
+content inset on the inverted stream list. Update that inset only when keyboard
+motion settles; never drive it per frame.
+
+Move the stream and composer together through `KeyboardDock`. Do not translate
+them independently.
+
+`KeyboardShiftProvider` owns the normalized shift used for settled insets and
+portal geometry, plus the `isMoving` worklet value. It reconciles native
+animation-end events because the controller can retain a nonzero value after
+the keyboard closes.
+
+Measure portal anchors while the dock is at rest. If a popover opens during
+motion, re-measure when `isMoving` settles. `measureInWindow` includes the
+dock's current layout and transform. Snapshot the shift at measurement time and
+apply only the subsequent shift delta to the animated `bottom`. Adding the full
+shift moves the portal twice and can place it over the composer controls.
 
 The provider also reconciles iOS from the controller's native `onEnd` event.
 The controller's stock iOS shared values update at move start and during an
@@ -155,10 +175,6 @@ leave the last height/progress pair stuck in either the open or closed state.
 Keep that terminal reconciliation on the UI thread; a later focus or blur must
 not be required to repair the offset.
 
-Re-measure on `Keyboard.addListener('keyboardDidShow'|'keyboardDidHide')` only
-to refresh the snapshot if the keyboard was mid-transition when the popover
-opened.
-
 ## Gotcha 4 — Host-relative positioning before platform offsets
 
 The generic anchored-overlay rule is: