[codex] Stabilize local workspace comments

[mussonking]

Summary

This PR stabilizes comment mode for local workspace previews and fixes a few related local-workspace edge cases found during manual testing.

What changed

• Saves comments independently from sending them to the agent.
• Adds an explicit “send to chat” queue so saved-only comments stay in the Comments panel until the user sends them.
• Reuses the existing pending comment for the same selection instead of creating duplicates.
• Reopens saved comments with their text prefilled from both the main preview and Files / App.jsx preview.
• Re-pins/highlights the target element when a saved comment is opened from the Comments panel.
• Closes stale comment bubbles when the underlying comment is deleted or when leaving the workspace view.
• Keeps stop/cancel from being undone by late generation stream events.
• Treats missing/renamed workspace watcher paths as recoverable so they do not surface as renderer errors.

Why

Local workspace comment mode had a few state mismatches between the preview iframe, saved comment rows, and the renderer store. These could leave the UI in stale states: saved comments not appearing in the bubble, duplicated comments on the same selection, deleted comments leaving an orphaned bubble, and saved comments opening without the target element highlighted.

Validation

• Full pre-push checks passed: workspace typecheck, lint, and full test suite.
• Targeted desktop tests passed around comments, preview panes, file previews, store behavior, cancellation, and file watcher recovery.
• Runtime overlay tests cover the saved-comment highlight path, including body-relative XPath selectors.
• Manual testing covered save, reopen, delete, add-to-chat, apply, stop, and leaving the workspace.