A1 Lease heartbeat: jobs::renew keeps a long-but-healthy job's lease fresh
so it is never stolen mid-flight nor inflated toward max_attempts.
A2 Stream chapter pages straight to storage (peak memory = one image) and
persist rows + page_count in one short transaction off the network path
(S3-ready); roll back stored blobs on failure via Storage::delete.
A3 ±20% jitter on exponential backoff to avoid a retry thundering herd.
A4 Outer per-dispatch timeout (CRAWLER_JOB_TIMEOUT_SECS, default 600) so a
hung job is acked-failed instead of wedging a worker.
A5 Metadata circuit-breaker (CRAWLER_METADATA_MAX_CONSECUTIVE_FAILURES,
default 10): abort a pass on a source outage without marking a clean exit,
so the next tick recovery-sweeps.
Adds CRAWLER_BROWSER_RESTART_THRESHOLD config (used by the upcoming
coordinated browser restart). Bumps version 0.52.0 -> 0.53.0.
Co-Authored-By: Claude Opus 4.8 <noreply@anthropic.com>
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