feat(w5): ship v2.0.0 platform sync, undo persistence, and updates

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

tests/main/undo-stack.test.ts

@@ -0,0 +1,33 @@
+import { describe, it, expect, beforeEach, afterEach } from 'vitest'
+import { DatabaseSync } from 'node:sqlite'
+import { migrate } from '../../src/main/db/migrate'
+import { UndoStackService } from '../../src/main/services/undo-stack.service'
+import { VolumeRepository } from '../../src/main/db/repositories/volume.repo'
+import { ChapterRepository } from '../../src/main/db/repositories/chapter.repo'
+import type { SqliteDb } from '../../src/main/db/types'
+
+describe('UndoStackService', () => {
+  let db: SqliteDb
+  let svc: UndoStackService
+  let chapterId: string
+
+  beforeEach(() => {
+    db = new DatabaseSync(':memory:')
+    migrate(db)
+    svc = new UndoStackService(db)
+    const vol = new VolumeRepository(db).create('卷一', 0)
+    chapterId = new ChapterRepository(db).create(vol.id, '第一章', 0).id
+  })
+
+  afterEach(() => {
+    db.close()
+  })
+
+  it('UT-UNDO-01: push and list undo entries', () => {
+    svc.push(chapterId, { type: 'doc', content: '<p>旧内容</p>' })
+    svc.push(chapterId, { type: 'doc', content: '<p>新内容</p>' })
+    const list = svc.list(chapterId)
+    expect(list).toHaveLength(2)
+    expect(list[0]?.operation.content).toContain('新内容')
+  })
+})