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>

tests/main/migrate-v7.test.ts

@@ -11,7 +11,7 @@ describe('migrate v7', () => {
     db = new DatabaseSync(':memory:')
     migrate(db)
     const version = db.prepare('SELECT MAX(version) AS v FROM schema_version').get() as { v: number }
-    expect(version.v).toBe(8)
+    expect(version.v).toBe(9)
     const tables = db
       .prepare("SELECT name FROM sqlite_master WHERE type='table' AND name='chapter_writing_snapshots'")
       .get()