A failed GET /api/v1/jobs/{id} no longer ends polling. useJob exposes the
request's error, keeps the last known status and result, and schedules the
next poll on the same 500 ms to 2 s backoff. Polling stops only at a
terminal status, a changed job id or unmount.
Co-Authored-By: Claude Opus 5.5 <noreply@anthropic.com>