feat(w2): add PackService for .novel and .novel-all export/import

Introduce pack-bootstrap chunk, ZipArchive-based PackService with progress IPC,
book registry import helpers, and IT-PACK-01 / IT-ALL-02 integration tests.

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

src/shared/ipc-channels.ts

@@ -150,5 +150,14 @@ export const IPC = {
   CHAPTER_TAG_REMOVE: 'chapter:tagRemove',
   BOOK_PREFS_GET: 'book:prefsGet',
   BOOK_PREFS_SET: 'book:prefsSet',
-  AI_SESSION_EXPORT: 'ai:sessionExport'
+  AI_SESSION_EXPORT: 'ai:sessionExport',
+  PACK_EXPORT_BOOK: 'pack:exportBook',
+  PACK_IMPORT_BOOK: 'pack:importBook',
+  PACK_EXPORT_ALL: 'pack:exportAll',
+  PACK_IMPORT_ALL: 'pack:importAll',
+  PACK_PICK_FILE: 'pack:pickFile',
+  PACK_ESTIMATE_EXPORT_ALL: 'pack:estimateExportAll',
+  PACK_CANCEL: 'pack:cancel',
+  PACK_NEEDS_CONFIRM: 'pack:needsConfirm',
+  PACK_PROGRESS: 'pack:progress'
 } as const