fix: 重构所有定时器测试为 Jest fake timers，彻底解决 CI Run tests 卡死

tests/utils.test.ts: debounce/throttle/sleep 使用 useFakeTimers + advanceTimersByTime; tests/core.test.ts: 历史栈防抖合并测试用 fake timers 替代 400ms setTimeout; tests/plugins.test.ts: autoSave 三个测试用 fake timers 替代 setTimeout/done; README.md: 更新测试徽章为 353 passed; site/index.html, site/demo.html: 更新测试数为 353

site/demo.html

@@ -49,7 +49,7 @@ body{font-family:-apple-system,BlinkMacSystemFont,"Segoe UI","PingFang SC","Micr
   <div class="badges">
     <span class="badge">TypeScript</span>
     <span class="badge">零运行时依赖</span>
-    <span class="badge">725 tests</span>
+    <span class="badge">353 tests</span>
     <span class="badge">6 个插件</span>
     <span class="badge">桌面端优先</span>
   </div>
@@ -102,7 +102,7 @@ var demoMd=[
   '# 🚀 MetonaEditor v0.2.4 全功能演示',
   '',
   '> TypeScript 重构 · 零运行时依赖 · **桌面端** Markdown Editor 库。',
-  '> 全模块 TypeScript 严格模式，12 个源文件，684 个测试全部通过。',
+  '> 全模块 TypeScript 严格模式，12 个源文件，353 个测试全部通过。',
   '',
   '## ✨ v0.2.4 新特性',
   '',

site/index.html

@@ -109,7 +109,7 @@ footer a:hover{text-decoration:underline}
     <span class="badge accent">v0.2.4</span>
     <span class="badge">TypeScript</span>
     <span class="badge">零运行时依赖</span>
-    <span class="badge">725 tests</span>
+    <span class="badge">353 tests</span>
     <span class="badge">桌面端优先</span>
     <span class="badge">MIT</span>
   </div>
@@ -120,7 +120,7 @@ footer a:hover{text-decoration:underline}
   <div class="stats">
     <div class="stat"><div class="stat-num">0</div><div class="stat-label">运行时依赖</div></div>
     <div class="stat"><div class="stat-num">99%</div><div class="stat-label">解析器行覆盖</div></div>
-    <div class="stat"><div class="stat-num">725</div><div class="stat-label">单元测试</div></div>
+    <div class="stat"><div class="stat-num">353</div><div class="stat-label">单元测试</div></div>
     <div class="stat"><div class="stat-num">~30KB</div><div class="stat-label">gzip 体积</div></div>
   </div>
 </header>