feat(i18n): tab auto titles follow the UI language

Titles are stored display text (layout templates, session snapshot,
broadcast registry), so a pane used to keep the wording of the language it
was opened in, and nextTerminalTitle could not even parse the number back
out of another language's pattern (numbering restarted, duplicates).

New pure module src/shared/terminalTitle.ts: resolution tries all four
languages' patterns, rendering uses the active one; i18n gains tFor(lang)
for off-language rendering. Workspace retitles auto-numbered local tabs in
place on language switch, snapshot restore and template apply; SSH panels
(user-typed connection names) are never touched. dockview's title-change
event propagates the new title to the broadcast registry and the snapshot
save with no extra wiring.

New test terminal-title.mjs (16 writer/reader language pairs, non-auto
title boundaries, gap filling); offline suite grows 17 -> 18.

docs/ROADMAP.md

@@ -146,7 +146,7 @@
 - [x] 归档脚本入 `scripts/`，`KEEP_TAG` 改必传参数
 - [x] `isPanicLockChord` 改判 `input.code`（物理键位，Dvorak/非拉丁布局正确）
 - [x] P3：设置页「更新通道」死控件移除、layoutMenu/IconRail memo + onOpenSettings useCallback、TerminalHandle 死 API 移除
-- [ ] 面板标题存已翻译字符串（切语言错位）——** deferred**：牵涉 5 个消费点 + 旧持久化数据兼容，另开一轮处理
+- [x] 面板标题存已翻译字符串（切语言错位）——✅ 已修：不改持久化格式，改多语言反解 + 语言切换/快照恢复/模板应用三处原地重渲染（`src/shared/terminalTitle.ts`，18 号测试 terminal-title）
 
 ## 工程约定（贯穿各阶段）