feat(tui): add Simplified Chinese UI translations and language selector

[fyihang]

Related Issue

N/A — this PR directly addresses the request to add a Chinese UI and language selection to the CLI TUI.

Problem

The Kimi Code CLI TUI was English-only. Users who prefer Simplified Chinese had no way to switch the interface language.

What changed

• Added a new i18n layer under �pps/kimi-code/src/tui/i18n/:

  • ypes.ts: Language, Translations, and typed translation keys.
    

  • �n.ts / zh.ts: English and Simplified Chinese translation catalogs.
  • index.ts: setLanguage, getLanguage, and (key, vars?).
• Persisted the language choice in TuiConfig via the existing config save/load path.
• Added /language slash command and wired it into the command dispatcher.
• Added a language picker dialog and surfaced it in Settings.
• Updated KimiTUI to apply the saved language on startup and on /reload.
• Internationalized the welcome panel, footer hints, settings labels, and theme selector labels.
• Added est/tui/i18n.test.ts and updated existing tests to include the new language field.

The approach keeps translations co-located with the TUI, uses the existing config persistence mechanism, and mirrors how theme selection is implemented.

Checklist

• I have read the CONTRIBUTING document.
• I have linked a related issue, or explained the problem above.
• I have added tests that prove my feature works.
• Ran gen-changesets skill, or this PR needs no changeset.
• Ran gen-docs skill, or this PR needs no doc update.

[changeset-bot]

🦋 Changeset detected

Latest commit: 4fcc7e3

The changes in this PR will be included in the next version bump.

This PR includes changesets to release 1 package

Name	Type
@moonshot-ai/kimi-code	Minor

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