feat: multi-language interface (zh-CN/zh-TW/en/ja), multilingual offline changelog, settings robustness

i18n
- shared/i18n: dependency-free t() with flat per-namespace dictionaries
  (common/settings/workspace/terminal/ssh/panels/main), zh-CN fallback
- language picker in Settings -> System; antd ConfigProvider locale follows it
- main process tracks the language too: tray menu, close prompt, ssh/sftp/
  zmodem errors and the log TUI marker are translated; tray rebuilds on change

changelog
- CHANGELOG.md (zh-CN canonical) + .zh-TW/.en/.ja, bundled via ?raw and read
  per interface language with per-version fallback to zh-CN (no network)
- sync-changelog.cjs merges RELEASE_NOTES[.<lang>].md per release; release.cjs
  refuses to publish without a zh-CN entry for the version

settings robustness
- closeAction 'ask' survives the sanitizer (was silently coerced to 'tray',
  which made the 'ask every time' option dead)
- highlight rules are repaired instead of dropped: string priority, 0/1
  enabled, missing fg colour; unknown fields preserved
- load-time warnings are written to settings-warnings.log (deduped, capped)

terminal/UI
- configurable terminal toolbar: open working directory (default on), session
  log recording (off), open logs folder (off)
- global shortcut field records key combos (modifier or F-key required)
- input suggestions + command history default to off, with a one-time reset
  migration for existing installs
- settings dialog scrolling fixed (antd v6 renamed the tabs container), theme
  gallery nested scrollbar removed, joined segmented pickers with readable
  selected-state text

tests: settings-store.mjs (15 checks) added; commands-store.mjs updated for
the new off-by-default history setting

src/shared/settings.ts

@@ -1,4 +1,5 @@
 import type { TerminalTheme } from './theme'
+import type { Language } from './i18n'
 
 /** One terminal keyword-highlight rule (regex → ANSI color injection). */
 export interface HighlightRule {
@@ -72,6 +73,8 @@ export interface SystemSettings {
    * to parsing typed `cd` commands.
    */
   shellIntegration?: boolean
+  /** interface language (see @shared/i18n); missing = 简体中文 */
+  language?: Language
 }
 
 export interface AppSettings {
@@ -133,5 +136,5 @@ export const DEFAULT_SETTINGS: AppSettings = {
   },
   customThemes: [],
   highlightRules: DEFAULT_HIGHLIGHT_RULES,
-  system: { launchAtLogin: false, preventSleep: false, globalShowHide: '', closeAction: 'tray', autoCheckUpdate: true, restoreSession: true, shellIntegration: false }
+  system: { launchAtLogin: false, preventSleep: false, globalShowHide: '', closeAction: 'tray', autoCheckUpdate: true, restoreSession: true, shellIntegration: false, language: 'zh-CN' }
 }