fix(tts): restore cross-section auto-page-turn during TTS playback (#4148)

When TTS playback crosses a section boundary, the page would stay on
the last page of the previous chapter while audio continued reading
the next chapter — leaving the user stuck behind the "back-to-TTS"
button.

Two compounding issues since the paginator adjacent-section preloading
landed:

1. `handleSectionChange` called `view.renderer.goTo(resolved)` without
   awaiting. `TTSController.#initTTSForSection` does
   `await this.onSectionChange?.(sectionIndex)` precisely so the view
   can finish navigating before audio of the new section starts, but
   the missing await defeated that contract.

2. `handleHighlightMark` returned silently on a cross-section
   mismatch (`viewSectionIndex !== ttsSectionIndex`), so when the
   renderer.goTo above completed only partially — which can happen on
   the new paginator when the target section is already loaded as an
   adjacent view and the post-goTo state appears reused without a
   visible page flip — there was no second chance to drag the view to
   the TTS cfi.

Fix:

- Await `view.renderer.goTo` in `handleSectionChange`.
- In `handleHighlightMark`, run the cross-section branch *before* the
  `followingTTSLocationRef` check and call `view.goTo(cfi)` directly,
  stamping `sectionChangingTimestampRef` so the back-to-TTS button
  stays suppressed while progress.location catches up. Skip only when
  the user is actively selecting text.

Adds unit tests covering both the cross-section navigation path and
the in-section scrollToAnchor path.

apps/readest-app/src/__tests__/hooks/useTTSControl.test.tsx

@@ -35,6 +35,7 @@ const mockView = {
   getCFI: vi.fn().mockReturnValue('cfi'),
   deselect: vi.fn(),
   resolveNavigation: vi.fn(),
+  goTo: vi.fn(),
   history: { back: vi.fn(), forward: vi.fn() },
   tts: {
     from: vi.fn().mockReturnValue('<speak>hello</speak>'),
@@ -241,3 +242,70 @@ describe('useTTSControl concurrent tts-speak events', () => {
     });
   });
 });
+
+describe('useTTSControl handleHighlightMark cross-section navigation', () => {
+  beforeEach(() => {
+    ttsControllerInstances.length = 0;
+    pendingInitResolvers.length = 0;
+    mockView.renderer.scrollToAnchor.mockClear();
+    mockView.renderer.goTo.mockClear();
+    mockView.goTo.mockClear();
+    mockView.resolveCFI.mockReset();
+    mockViewSettings.ttsLocation = null;
+  });
+
+  afterEach(() => {
+    cleanup();
+  });
+
+  const setupAndCaptureHighlightHandler = async () => {
+    render(<Harness />);
+
+    await act(async () => {
+      const p = eventDispatcher.dispatch('tts-speak', { bookKey: 'book-1' });
+      for (let i = 0; i < 10; i++) await Promise.resolve();
+      while (pendingInitResolvers.length > 0) pendingInitResolvers.shift()!();
+      await p;
+    });
+
+    // Let the listener-registration useEffect run.
+    await act(async () => {
+      for (let i = 0; i < 5; i++) await Promise.resolve();
+    });
+
+    const controller = ttsControllerInstances[0] as {
+      addEventListener: { mock: { calls: [string, (e: Event) => void][] } };
+    };
+    const calls = controller.addEventListener.mock.calls;
+    const entry = calls.find(([name]) => name === 'tts-highlight-mark');
+    if (!entry) throw new Error('tts-highlight-mark listener was not registered');
+    return entry[1];
+  };
+
+  it('navigates to the cfi via view.goTo when TTS crosses into a new section', async () => {
+    const handler = await setupAndCaptureHighlightHandler();
+
+    // primaryIndex is 0 (current view section). Make the TTS cfi resolve to section 1.
+    mockView.resolveCFI.mockReturnValue({ index: 1, anchor: () => new Range() });
+
+    await act(async () => {
+      handler(new CustomEvent('tts-highlight-mark', { detail: { cfi: 'epubcfi(/6/8!/4/2)' } }));
+    });
+
+    expect(mockView.goTo).toHaveBeenCalledWith('epubcfi(/6/8!/4/2)');
+    expect(mockView.renderer.scrollToAnchor).not.toHaveBeenCalled();
+  });
+
+  it('keeps in-section behaviour: scrolls via renderer without navigating', async () => {
+    const handler = await setupAndCaptureHighlightHandler();
+
+    mockView.resolveCFI.mockReturnValue({ index: 0, anchor: () => new Range() });
+
+    await act(async () => {
+      handler(new CustomEvent('tts-highlight-mark', { detail: { cfi: 'epubcfi(/6/4!/4/2)' } }));
+    });
+
+    expect(mockView.renderer.scrollToAnchor).toHaveBeenCalledTimes(1);
+    expect(mockView.goTo).not.toHaveBeenCalled();
+  });
+});

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

@@ -187,13 +187,6 @@ export const useTTSControl = ({ bookKey, onRequestHidePanel }: UseTTSControlProp
       viewSettings.ttsLocation = cfi;
       setViewSettings(bookKey, viewSettings);
 
-      if (!followingTTSLocationRef.current) return;
-
-      const docs = view.renderer.getContents();
-      if (docs.some(({ doc }) => (doc.getSelection()?.toString().length ?? 0) > 0)) {
-        return;
-      }
-
       const hlContents = view.renderer.getContents();
       const hlPrimaryIdx = view.renderer.primaryIndex;
       const { doc, index: viewSectionIndex } = (hlContents.find((x) => x.index === hlPrimaryIdx) ??
@@ -204,6 +197,27 @@ export const useTTSControl = ({ bookKey, onRequestHidePanel }: UseTTSControlProp
 
       const { anchor, index: ttsSectionIndex } = view.resolveCFI(cfi);
       if (viewSectionIndex !== ttsSectionIndex) {
+        // TTS crossed into a new section before the view caught up. The
+        // `await onSectionChange` path in TTSController fires renderer.goTo
+        // via handleSectionChange, but the new paginator's #goTo can resolve
+        // before the visible page actually flips when the target section is
+        // already preloaded as an adjacent view — leaving the user stuck on
+        // the last page of the previous chapter while audio continues. Drive
+        // navigation from the highlight cfi directly, stamping the timestamp
+        // so the "back-to-TTS" button stays suppressed while progress.location
+        // catches up. Skip only when the user is actively selecting text.
+        if (hlContents.some(({ doc }) => (doc.getSelection()?.toString().length ?? 0) > 0)) {
+          return;
+        }
+        sectionChangingTimestampRef.current = Date.now();
+        followingTTSLocationRef.current = true;
+        view.goTo?.(cfi);
+        return;
+      }
+
+      if (!followingTTSLocationRef.current) return;
+
+      if (hlContents.some(({ doc }) => (doc.getSelection()?.toString().length ?? 0) > 0)) {
         return;
       }
 
@@ -363,7 +377,9 @@ export const useTTSControl = ({ bookKey, onRequestHidePanel }: UseTTSControlProp
       if (!sections || sectionIndex < 0 || sectionIndex >= sections.length) return;
       sectionChangingTimestampRef.current = Date.now();
       const resolved = view.resolveNavigation(sectionIndex);
-      view.renderer.goTo?.(resolved);
+      // Await so TTSController's `await onSectionChange` doesn't proceed to
+      // speak the new section before the view has finished navigating to it.
+      await view.renderer.goTo?.(resolved);
     },
     [bookKey, getView],
   );