Review corrections on the observation record:
- `pumpJobOutput` subscribes to `done` once and keeps one pending timer;
racing the same pending promise every poll round retained a reaction
per round for the life of the job.
- The `ctx.jobOutput` effect disposer is async and awaits every open
carrier's `dispose()`, so the fiber reports unloaded only once the old
iterators are quiescent.
- `SessionJob.record: true` replaces `outputTotal`: `append` never commits
a roster change, so the mirrored count was stale while output flowed;
the live offsets ride the observation stream's `opened` anchor.
- The record is documented as a best-effort live preview whose
cross-stream reordering is bounded by the poll interval.
- The web e2e scenarios hold their background job on a test-owned barrier
file instead of a wall-clock sleep, and each is one test rather than a
chain sharing a job id.
Yichen Jiang
761282724b