feat(todo): auto-cleanup stale todos + /clear-tasks command

[LifetimeVip]

Description

This feature adds automatic cleanup of stale (completed/cancelled) todos and introduces two new slash commands to manage active tasks.

Changes

1. Auto-cleanup: Completed/cancelled todos are filtered out before saving (in todowrite.txt tool) and on session load (in session/todo.ts). Only pending and in_progress tasks are preserved.

2. New slash commands:

   • /clear-tasks — Clears all active tasks at once (English name)
   • /清除任务 — Same functionality, Chinese name for Chinese-language users

3. i18n: Added Chinese translations in zh.ts for the new command descriptions and category.

Files changed

• packages/opencode/src/tool/todowrite.txt — Updated description to mention auto-removal
• packages/opencode/src/session/todo.ts — Filter out completed/cancelled tasks on load
• packages/opencode/src/command/index.ts — Register new slash commands
• packages/app/src/i18n/zh.ts — Chinese translations for new commands

Why this change

Stale todos accumulate in the chat UI and persist across conversations. This change keeps the todo list clean automatically and gives users a quick way to reset tasks.

Verification

• npm run typecheck — zero errors
• npm test — 62/62 all passing
• Manual test: todos are filtered correctly on reload

[github-actions]

This issue doesn't fully meet our contributing guidelines.

What needs to be fixed:

• The title should start with [FEATURE]: for feature requests (e.g. [FEATURE]: auto-cleanup stale todos + /clear-tasks command)
• The issue doesn't use the Feature Request template — please include the required verification checkbox confirming this feature hasn't been suggested before
• The issue reads like a pull request description (lists files changed, test results, etc.) rather than a feature request. Please describe the problem/need you're trying to solve and what the desired behavior should be, without implementation details

Please edit this issue to address the above within 2 hours, or it will be automatically closed.

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This issue might be a duplicate of existing issues. Please check:

• [FEATURE]: add /clear slash command to clear conversation in the same session (similar to claude code) #19499: Proposes a /clear slash command for clearing conversation/session context — overlapping with the slash command aspect of this request

If you believe this was flagged incorrectly, please let a maintainer know.

[github-actions]

This issue has been automatically closed because it was not updated to meet our contributing guidelines within the 2-hour window.

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