feat: ship v1.2.0 Wave 1 foundation with book settings, chapter management, and focus mode

Deliver schema v9, book/chapter IPC extensions, BookSettingsTab, chapter meta/tags,
AI session menu, focus mode and TTS, template context enrich, and Wave 1 E2E coverage.

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

src/renderer/components/settings/SettingsPage.tsx

@@ -252,7 +252,7 @@ export function SettingsPage(): React.JSX.Element {
         {section === 'shortcuts' && <ShortcutEditor />}
         {section === 'about' && (
           <p style={{ color: 'var(--text-secondary)', lineHeight: 1.8 }}>
-            {t('app.name')} v1.1.0
+            {t('app.name')} v1.2.0
             <br />
             {t('app.tagline')}
           </p>