fix(app): activate mobile panels after motion settles

Gesture previews were publishing React presentation state and activating retained content before the native motion finished. Keep transient motion on the UI thread and publish the active panel only from the accepted animation completion.

docs/mobile-panels.md

@@ -30,8 +30,10 @@ The UI worklet owns transient motion:
 - the active gesture's starting revision
 - the last settled target
 
-React also owns presentation lifecycle: whether an overlay is mounted/displayed and whether it may
-receive pointer events. Worklets never own `display` or `pointerEvents`.
+React publishes the active panel only after its motion reaches the final anchor. Retained content
+never observes gesture previews, progress, or an unsettled target. The gesture hosts stay mounted;
+worklets reveal their retained overlays through native styles while React owns pointer events and
+accessibility.
 
 ## Why one position
 
@@ -85,8 +87,8 @@ definition, no longer eligible to begin.
 - Animated panel nodes use React Native static styles plus inline theme values. Do not attach
   Unistyles-generated styles to those nodes; Unistyles and Reanimated patching the same Fabric node
   has caused native crashes.
-- The plain React wrapper owns `display: none` after settlement. This prevents a stale Fabric animated
-  prop commit from resurrecting a closed overlay.
+- Gesture start and progress must not update React state. The retained overlay is already mounted and
+  offscreen; only the shared position and its derived native styles move during a drag.
 - Hidden tabs and workspaces use `RetainedPanel`. It owns a non-collapsible native root, visibility,
   pointer events, and the active signal consumed by `useRetainedPanelActive`.
 - Panels whose gesture wrapper already owns visibility use `RetainedPanelActivity` to provide the
@@ -98,8 +100,8 @@ definition, no longer eligible to begin.
 - Retention order and render order are separate concerns. LRU metadata may change on every switch;
   keyed retained roots must keep a stable sibling order. Moving large retained roots triggered Fabric
   Differ failures (`addViewAt` / `removeViewAt` view reuse) on Android.
-- The newly active panel must be included in the same render that changes selection. Adding it from an
-  effect creates a committed frame where every retained panel is hidden, which is a real blank screen.
+- `useIsMobilePanelActive` follows the settled target, not the requested target. Activation work may
+  begin only after the finishing animation completes; cancellation publishes nothing.
 - Do not suspend retained native subtrees with `Suspense`/`react-freeze`. Suspension changes native
   ownership and can detach descendants. Keep the tree mounted, stabilize its subscriptions/selectors,
   and use the retained-panel active signal to stop timers, polling, and other genuine background work.