fix(reader): gate route View Transitions on API support (READEST-9) (#4989)

* fix(reader): gate route View Transitions on the API, turns on groups (READEST-9)

Reverts #4949, which opened books through the plain router to dodge the
"Transition was aborted because of timeout in DOM update" TimeoutError
(Sentry READEST-9). Rather than carve the transition out of one flow, gate it
at the router: useAppRouter routes through the View Transition router only
where the engine has the View Transitions API, and every into-reader path
(including the reverted ones) goes back through useAppRouter.

The base View Transitions API and nested view-transition groups reach very
different browsers, so they become two separate appService capability flags,
each backed by a probe in utils/viewTransition:

* supportsViewTransitionsAPI (document.startViewTransition): the baseline a
  route crossfade needs, landing on Chrome 111+, Safari 18+, recent WebView.
  Gates the router.
* supportsViewTransitionGroup (view-transition-group: nearest, Chrome/WebView
  140+): the far narrower target the paginator's layered turns require. Gates
  the turn-style options and the captured-turn fallback.

Both flags fold in the Linux WebKitGTK carve-out because it crashes on the
snapshot, matching the supportsCanvasContext2DFilter precedent.

Co-Authored-By: Claude Opus 4.8 (1M context) <noreply@anthropic.com>

* fix(tts): enlarge the Now Playing bar and scale its controls responsively

Grow the collapsed bar to h-14 with a 10x10 cover and symmetric px-2 padding,
drive the play/pause and close icons through useResponsiveSize instead of fixed
pixel sizes, and cut the bottom safe-area contribution to a third so the bar
sits closer to the screen edge.

Co-Authored-By: Claude Opus 4.8 (1M context) <noreply@anthropic.com>

---------

Co-authored-by: Claude Opus 4.8 (1M context) <noreply@anthropic.com>

apps/readest-app/src/app/reader/hooks/useCapturedTurn.ts

@@ -5,6 +5,7 @@ import { useBookDataStore } from '@/store/bookDataStore';
 import { useReaderStore } from '@/store/readerStore';
 import { captureWebviewRegion } from '@/utils/bridge';
 import { isTauriAppPlatform } from '@/services/environment';
+import { detectViewTransitionGroup } from '@/utils/viewTransition';
 import { CapturedPageTurn, CapturedTurnStyle } from '../utils/capturedTurn';
 import { useTouchInterceptor } from './useTouchInterceptor';
 
@@ -13,21 +14,6 @@ import { useTouchInterceptor } from './useTouchInterceptor';
 // take over where the engine supports them, push everywhere else.
 let captureBroken = false;
 
-/**
- * Whether the engine runs the paginator's layered View Transition turns
- * reliably. iOS 18 WebKit ships `document.startViewTransition` but crashes
- * the WebContent process when a turn transition snapshots the reader, so
- * the presence of the API is not enough; nested view-transition groups
- * (Chrome/WebView 140+) mark the mature engines where the layered turns
- * are known to work.
- */
-export const supportsViewTransitionTurns = (): boolean =>
-  typeof document !== 'undefined' &&
-  'startViewTransition' in document &&
-  typeof CSS !== 'undefined' &&
-  typeof CSS.supports === 'function' &&
-  CSS.supports('view-transition-group', 'nearest');
-
 /**
  * The turn style the captured-page pipeline should drive for this view, or
  * null when the paginator's own turns apply. The pipeline needs a native
@@ -46,7 +32,7 @@ export const getCapturedTurnStyle = (
     return null;
   }
   if (viewSettings.pageTurnStyle === 'curl') return 'curl';
-  if (viewSettings.pageTurnStyle === 'slide' && !supportsViewTransitionTurns()) return 'slide';
+  if (viewSettings.pageTurnStyle === 'slide' && !detectViewTransitionGroup()) return 'slide';
   return null;
 };
 
@@ -66,7 +52,7 @@ export const applyPageTurnAttributes = (
 ) => {
   const captured = getCapturedTurnStyle(viewSettings, isFixedLayout);
   const style = viewSettings.pageTurnStyle;
-  if (style && style !== 'push' && !captured && supportsViewTransitionTurns()) {
+  if (style && style !== 'push' && !captured && detectViewTransitionGroup()) {
     view.renderer.setAttribute('turn-style', style);
   } else {
     view.renderer.removeAttribute('turn-style');