Process looked at its context only while it waited for a processing
slot, so a transcode went on decoding and encoding, holding its slot,
however long after its request's downstream_timeout that took.
acquireSlot now gives the slot back and returns the context's error
when the context has ended by the time it has a slot, and encode
returns that error without beginning. libvips cannot stop an encode
once it has begun, so that encode keeps its slot until it finishes.
README.md gives how long that can take per output format at the 8192
limits and no longer says the work stops when downstream_timeout ends;
TODO.md is corrected the same way.
Model: opus-5-5
clawbot
639a86a4a8