Report aborted turns honestly instead of surfacing the model's preamble

[patriyang]

Closes #88

Root cause

Not a phantom interrupt. The plugin's own idle stall watchdog fired. Confirmed from the three failing jobs' log files:

[2026-08-06T08:36:50.822Z] Codex turn stalled (idle): no activity for 900s. Interrupting and aborting the turn.

DEFAULT_TURN_STALL_TIMEOUT_MS is 15 min; the rollouts show 15m01s, 21m00s and 21m06s of complete notification silence before the abort. handleStall calls turn/interrupt, and Codex records every interrupt as turn_aborted / reason: "interrupted" regardless of who issued it — which is why it read as a user cancellation. Two of the three went silent within six seconds of each other on independent turns, which points at an upstream stall rather than the model thinking. The watchdog did its job and is unchanged here.

The duration_ms in the turn_aborted event (247070) is also not the wall clock — completed_at - started_at is 1434s for that same turn — so the coincidence with the 240s status-wait timeout noted in the issue was a red herring.

The actual defect

Everything wrong here is in how the aborted turn is reported:

• executeTaskRun set rawOutput = result.finalMessage unconditionally. finalMessage is turnState.lastAgentMessage, so on an aborted turn it is the model's opening narration — well-formed prose that /codex:implement parses as the report body.
• The task JSON payload carried no failure field at all. The stall reason reached only the job log file, never stdout, the payload, or the stored result — renderTaskResult returns rawOutput whenever it is non-empty, so it shadowed the failure message too.

Fix

• rawOutput is gated on turn completion (result.status === 0). An incomplete turn's last agent message moves to a new partialOutput field, so every downstream consumer that keys off rawOutput correctly sees "no report".
• The task payload now carries partialOutput and failureMessage.
• renderTaskResult leads with the failure reason, lists the files the run already modified, and reproduces the partial text under a heading that says plainly it is not the final report. Completed turns render byte-identically to before.
• Same completion gate on the structured review path, so an aborted review cannot yield a verdict parsed out of a preamble. The raw text stays in payload.codex.stdout.
• implement.md now warns the controller that a failed dispatch may have already applied edits: check touchedFiles / git status and resume with --resume-id instead of re-dispatching fresh.

Verification

The first commit is a failing repro, committed before any product change:

• tests/fake-codex-fixture.mjs gains an idle-hung-turn-after-preamble behavior — emits a non-final agentMessage plus a fileChange, then goes silent until the idle watchdog fires.
• tests/runtime.test.mjs drives a real end-to-end task --write run against it. Before the fix it failed with rawOutput equal to the preamble; after, rawOutput is empty, partialOutput holds the preamble, failureMessage holds the stall reason, and touchedFiles still reports the edit that landed.
• tests/render.test.mjs pins both branches of renderTaskResult, including exact-string equality on the completed-turn path.

Full suite: 303 passed, 0 failed (node --test --test-concurrency=1 tests/*.test.mjs).

Codex SDD reviewers: spec SPEC_COMPLIANT, code quality APPROVED.

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