fix(app): recover failed turn retractions without duplicating drafts

[asfires]

What Changed

• Use Codex thread/revert when reverting a specific turn, with fallback support for older app-server versions.
• Verify rollback results from the mutation response to avoid failures caused by lagging thread reads.
• Prevent unresolved mid-thread retractions from being moved into new-thread drafts.
• Add focused server and web regression tests.

Why

Failed or delayed retraction acknowledgements could leave recovery pending, repeatedly roll back the same provider turn, or duplicate a message as a new-thread draft. This change uses the provider’s direct revert response when available, preserves compatibility with older Codex versions, and limits draft recovery to first-message retractions where it is appropriate.

UI Changes

No visible UI changes. The web change updates retraction recovery behavior only.

Checklist

• This PR is small and focused
• I explained what changed and why
• I included before/after screenshots for any UI changes
• I included a video for animation/interaction changes