POST /video/direct/init|complete: the browser seals (SPENC2) and PUTs
straight to object storage; the api HEAD-checks, registers the unprobed
asset and queues a probe job — video bytes never cross the api box.
Worker side: produce_job_claim widened to probe jobs (042), the runner
gains a probe lane (sealed fetch → SPENC1/SPENC2 open by magic → scratch →
ffprobe → metadata write-back → complete 100), worker storage reads SPENC2
frames via DIRECT_EC_PRIVATE_KEY (inherited through compose appenv), and a
ported ffprobe util. Probe rows carrying input_json fail instead of
stranding; the claim guard no longer strands probe rows as invalid.
