- Autocache range jobs now post at Background priority
(submit_video_background): they used to go through the Seek path and,
after the M4 seek over-admission, jumped ahead of playback and past the
render-queue bound. The interactive single-frame preview keeps Seek.
- Job.cancelled: the arena installs the slot's cancel atom, and
execute_job finishes a cancelled job with Error::State before running
the producer — a cancel no longer burns a full render/GPU pass only to
discard the result. Exactly-once delivery is unchanged.
- DECODE_LRU_CAP 8 -> 2: the decode service's LRU is a hand-off buffer,
not the cache of record (the eval-side decoded_frames LRU is); the
double-cache footprint at 1080p F32 drops by ~6 frames. A hand-off miss
is served from the eval cache without a new decode.
- Tests: sequence-aware preview cancel, over-admitted seek ordering,
deterministic prefetch LRU reuse, cancelled-job skip, autocache
priority. docs §3.4 backfilled with the A/B/C audit outcomes.