feat(ext): rerun tasks from history

[Adonis0123]

What

Add a rerun action for saved extension history tasks so users can execute the same task again without copying the original prompt manually.

Implementation notes:

• reuse a shared runTask() path in the sidepanel so chat submit and history rerun go through the same execute flow
• add Run again actions in both the history list and history detail views
• disable rerun while the agent is already running to avoid overlapping executions
• tighten history row keyboard handling so Enter or Space on nested action buttons does not open the detail view accidentally

This stays within the extension UI and does not change storage schema or agent execution semantics.

Type

• Bug fix
• Feature / Improvement
• Refactor
• Documentation
• Website
• Demo / Testing
• Breaking change

Testing

• Tested in modern browsers
• No console errors
• Types/doc added

Validated locally with:

• npx eslint packages/extension/src/entrypoints/sidepanel/App.tsx packages/extension/src/components/HistoryList.tsx packages/extension/src/components/HistoryDetail.tsx
• npm run lint
• npm run build
• npm run build:ext

I did not run a manual browser-side smoke test in this environment, so the browser checkbox is intentionally left unchecked.

Closes #304

Requirements / 要求

• I have read and follow the Code of Conduct and Contributing Guide . / 我已阅读并遵守行为准则。
• This PR is NOT generated by a bot or AI agent acting autonomously. I have authored or meaningfully reviewed every change. / 此 PR 不是由 bot 或 AI 自主生成的，我已亲自编写或充分审查了每一处变更。

Note

Keeping this PR as draft until human review is completed.

[Adonis0123]

Supplemental validation update:

• npm run lint passed
• npm run build passed
• npm run build:ext passed

I still did not run a manual browser-side smoke test in this environment, so that part remains pending for human verification.

[gaomeng1900]

Thanks for your contribution!

Looks good to me.

I adjusted the UI a little bit to be more consistent. Also removed rerunDisabled to stay simple.

Ready to merge.