## Why
Retrying a safety-buffered turn by rolling back the active thread rewrites the
source conversation and requires the TUI to repair its local transcript state.
## What changed
- Interrupt the buffered turn, then fork after the preceding completed turn and
submit the prompt on the new thread with the faster model and low reasoning
effort.
- Start a new thread when the buffered request is the conversation's first turn.
- Preserve committed steering input in the retry, leave the source thread
intact, and restore the prompt alongside any existing draft if branching
fails.
- Do not offer the retry action for side conversations or stale and in-progress
turns.
## Testing
Added coverage for retries with prior context, first-turn retries, committed
steering input, branch failures, existing composer drafts and attachments, and
side conversations.
GitOrigin-RevId: adb49da8236e9212ef0082e033e6f715986b5cd9
Felipe Coury
9cddda7556