feat: 实现笔临 P0/P1 Electron 桌面应用 v0.1.0

交付写作核心（TipTap、自动保存、分卷分章）、Onboarding、7 主题与双语 i18n、快捷键设置；主进程使用 node:sqlite；补全 Vitest 与 Playwright E2E；统一 design/ 目录并移除 desigin 拼写错误路径。

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

tests/main/word-count.test.ts

@@ -0,0 +1,12 @@
+import { describe, it, expect } from 'vitest'
+import { countWords } from '../../src/main/services/word-count'
+
+describe('countWords', () => {
+  it('counts CJK characters excluding whitespace', () => {
+    expect(countWords('林远深吸一口气')).toBe(7)
+  })
+
+  it('returns 0 for empty', () => {
+    expect(countWords('')).toBe(0)
+  })
+})