Prevent Chat retries and delayed Enter from submitting terminal drafts #41

Chat sends terminal input separately from the agent's recorded user message. A lost response, a permission/state transition during the paste delay, or a stalled PTY writer needs explicit handling so retries cannot paste twice or submit an uncertain draft.

A deterministic reproducer needs no account or network provider:

1. Start a synthetic PTY helper through the daemon and show a free composer.
2. Deliver a message while holding its FIFO writer; wait for the five-second write deadline.
3. Request another message with a new delivery key, then release the writer.
4. Verify the later request cannot enqueue Enter behind the expired paste. Retrying the original key must retain its interrupted result without additional input.

Another reproducer changes the helper's hook state to waiting after paste and before Enter, then back to done. Automatic Enter must still be cancelled. A deterministic terminal mutex test covers a competing raw redraw at screen-check/enqueue.

The proposed contribution adds per-run delivery keys, atomic readiness/enqueue, paste write-completion settling, interrupted-paste quarantine and full transcript matching in Chat. Manual terminal input remains available; program replacement creates a fresh automatic-delivery ledger.

Base: cd071c6. Candidate: 1255f94.

This does not establish the cause of earlier intermittent native failures, guarantee native consumption, or certify authenticated fresh/resume/fork/clear/account lifecycles. Enqueue, successful PTY write and recorded UserMessage are separate observations.