fix(updater,i18n): 对抗性审查修复（1中 + 3低）

- [中] 手动检查不再丢弃「已下载」事实：runCheck('manual') 原来无条件清
  抑制记录，导致下载完成后点「检查更新」会把关于页从「重启安装」退回
  「下载」（包已在磁盘）。改为保留 downloaded 记录，只清 announcement
  记账；测试 §19 补 manual-check 保持 downloaded 的口径（153 断言）
- website 首帧脚本：?lang= 的 decodeURIComponent 包 try/catch（畸形转义
  会在 IIFE 内抛 URIError，跳过 html[lang] 与防闪标记，指定语言被静默
  忽略）；zh-Hant-TW/zh-Hant-HK/zh-Hant 按 BCP-47 语义判为繁体
  （normalize 与 i18n-apply.js 双处同步）
- ZmodemOffers 是 App 兄弟节点，语言切换时父级 children bailout 不重渲染：
  订阅 language 并以 tFor 显式翻译（事件回调内的 t() 保留）
- ROADMAP 补录对抗性审查推迟项（周期检查可被设置写入推迟、启动开关
  即时生效语义、下载无整体超时、--channel-only/--skip-gitea 矛盾）

tests/updater-fallback.mjs

@@ -986,6 +986,28 @@ console.log('a finished download stays finished')
     ok(s.status === 'available', `a different release starts from 'available' (got '${s.status}')`)
     ok(s.version === '4.4.2', `and is named (${s.version})`)
   }
+
+  // A manual check after a finished download must ALSO keep the downloaded
+  // state — the package is on disk, so "downloaded" is the truthful answer, and
+  // folding the install button back into "download" would make the user fetch
+  // what they already have. The manual record drop only discards announcement
+  // bookkeeping, never the on-disk fact.
+  live.emit('update-downloaded', { version: '4.4.2' })
+  await tick()
+  ok(call(Ipc.UPDATE_STATE_GET).status === 'downloaded', 'the new release finishes too')
+  ctl.checkForUpdates = () => {
+    live.emit('checking-for-update')
+    live.emit('update-available', { version: '4.4.2' })
+    return Promise.resolve(null)
+  }
+  {
+    const state = await call(Ipc.UPDATE_CHECK)
+    ok(
+      state.status === 'downloaded' && state.version === '4.4.2',
+      `a manual check keeps a finished download finished (got '${state.status}')`
+    )
+    ok(state.status !== 'checking', 'and is not parked on the spinner')
+  }
 }
 
 console.log('balloons respect the visible-window guard')