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）

src/main/updater.ts

@@ -323,11 +323,17 @@ async function performCheck(source: CheckSource): Promise<UpdateState> {
  */
 export function runCheck(source: CheckSource = 'manual'): Promise<UpdateState> {
   // A manual check is an explicit act, so whatever it finds counts as news even
-  // if this run has already dealt with that version: the suppression record is
-  // dropped here — before the in-flight guard, so a click that joins a check
-  // already running gets the same treatment. (A manual DOWNLOAD needs no
-  // equivalent: its entry point never consults the record.)
-  if (source === 'manual') actedRelease = undefined
+  // if this run has already announced that version: the announcement half of the
+  // record is dropped here — before the in-flight guard, so a click that joins a
+  // check already running gets the same treatment. The DOWNLOADED half is kept:
+  // for a release whose package sits on disk, "downloaded" *is* the truthful
+  // answer, and dropping it made update-available report `available` again —
+  // folding the About tab's install button back into "download" for a manual
+  // check on an already-fetched release. (A manual DOWNLOAD needs no equivalent:
+  // its entry point never consults the record.)
+  if (source === 'manual') {
+    actedRelease = actedRelease?.downloaded ? actedRelease : undefined
+  }
   if (checkInFlight) return checkInFlight
   const task = performCheck(source)
   checkInFlight = task

src/renderer/src/workspace/ZmodemOffers.tsx

@@ -1,7 +1,8 @@
 import { useCallback, useEffect, useRef, useState } from 'react'
 import { App as AntdApp, Button, Modal, Space, Typography } from 'antd'
 import type { ZmodemOfferEvent, ZmodemResponse } from '@shared/ipc'
-import { t } from '@shared/i18n'
+import { DEFAULT_LANGUAGE, t, tFor } from '@shared/i18n'
+import { useSettingsStore } from '../settings/store'
 
 /**
  * M6 ZMODEM offer/done UX: renders one dialog per active zmodem offer.
@@ -15,6 +16,10 @@ import { t } from '@shared/i18n'
  */
 export default function ZmodemOffers(): null | React.JSX.Element {
   const { message } = AntdApp.useApp()
+  // Rendered as App's sibling: a language switch re-renders App, but the parent's
+  // children element is identical, so this subtree bails out and would keep the
+  // old language. Subscribe here and translate with the explicit language.
+  const language = useSettingsStore((s) => s.settings.system.language ?? DEFAULT_LANGUAGE)
   const [offers, setOffers] = useState<Map<string, ZmodemOfferEvent>>(new Map())
   const busyRef = useRef<Set<string>>(new Set())
 
@@ -117,21 +122,21 @@ export default function ZmodemOffers(): null | React.JSX.Element {
       closable={false}
       maskClosable={false}
       keyboard={false}
-      title={isReceive ? t('ssh.zmodem.titleReceive') : t('ssh.zmodem.titleSend')}
+      title={isReceive ? tFor(language, 'ssh.zmodem.titleReceive') : tFor(language, 'ssh.zmodem.titleSend')}
       footer={
         <Space>
           <Button
             type="primary"
             onClick={() => (isReceive ? void handlePickDir(first.id) : void handlePickFiles(first.id))}
           >
-            {isReceive ? t('ssh.zmodem.pickDir') : t('ssh.zmodem.pickFiles')}
+            {isReceive ? tFor(language, 'ssh.zmodem.pickDir') : tFor(language, 'ssh.zmodem.pickFiles')}
           </Button>
-          <Button onClick={() => handleCancel(first.id)}>{t('common.cancel')}</Button>
+          <Button onClick={() => handleCancel(first.id)}>{tFor(language, 'common.cancel')}</Button>
         </Space>
       }
     >
       <Typography.Text>
-        {isReceive ? t('ssh.zmodem.receiveDesc') : t('ssh.zmodem.sendDesc')}
+        {isReceive ? tFor(language, 'ssh.zmodem.receiveDesc') : tFor(language, 'ssh.zmodem.sendDesc')}
       </Typography.Text>
     </Modal>
   )