Same criterion as the last two: `vaapi.rs`'s sites are pointer dereferences and libav ctx calls,
not ash, so a proof here carries an argument. Three regions, three arguments.
`VaapiHw::new` also loses its `unsafe fn` outright, and the contrast with its CUDA twin is the whole
point: `CudaHw::new` keeps the marker because it is HANDED a `CUcontext` the caller must vouch for,
while this one takes four scalars and opens the VAAPI device itself. Two functions of near-identical
shape, opposite answers, decided by whether a caller can supply something broken.
The other two regions keep their markers (`open_vaapi_encoder`/`_mode` are handed raw
`*mut AVBufferRef`s) and gain the proofs they lacked. The encoder-config block now records the fact
that makes it sound rather than obvious: `av_buffer_ref` returns a NEW reference the codec context
adopts, so the callee shares the caller's device/frames buffers instead of consuming them — which is
also why the low-power entrypoint ladder can retry with the same two pointers after a failed attempt.
The frames-pool block reuses the `CudaHw::new` argument: alloc returns null-or-initialized and
`AvBuffer::from_raw` rejects null, so the `?` leaves before any field store can run.
One call site dropped its `unsafe {}` and its comment with it — the comment argued that libav was
initialized, which is a real precondition of the call but not one a caller can violate, so it is now
a note rather than a contract.
14 fenced files -> 11. Verified on .21 (fmt + both CI clippy steps rc=0) and, because this is the
live VAAPI construct path rather than dead code, ON THE AMD 780M (.116, pf-build distrobox):
`vaapi_cpu_encode_smoke`, `dmabuf_inner_alloc_drop_cycles` and `vaapi_probe_smoke` all pass —
3 passed / 0 failed, H265 + AV1 probes still true in both 8- and 10-bit.
enricobuehler
8e7ba00d2d