feat(w3): add continuous read mode and Wave 3 plan

Introduce ReadModeOverlay with device width and font theme persistence, sidebar and volume menu entry, plus E2E-READ-01 through 03.

Co-authored-by: Cursor <cursoragent@cursor.com>

src/renderer/App.tsx

@@ -19,6 +19,7 @@ import { SearchModal } from '@renderer/components/search/SearchModal'
 import { InspirationModal } from '@renderer/components/inspiration/InspirationModal'
 import { ImportBookModal } from '@renderer/components/import/ImportBookModal'
 import { ExportAllModal } from '@renderer/components/export/ExportAllModal'
+import { ReadModeOverlay } from '@renderer/components/read/ReadModeOverlay'
 import { FocusModeOverlay } from '@renderer/components/focus/FocusModeOverlay'
 import { NamingCheckModal } from '@renderer/components/ai/NamingCheckModal'
 import { useSearchStore } from '@renderer/stores/useSearchStore'
@@ -206,6 +207,7 @@ function AppInner(): React.JSX.Element {
         {view === 'settings' && <SettingsPage />}
       </div>
       <FocusModeOverlay />
+      <ReadModeOverlay />
       {showOnboarding && <OnboardingWizard onComplete={handleOnboardingComplete} />}
       <SearchModal />
       <InspirationModal />