`vk_av1_encode.rs` and `vk_valve_rgb.rs` are hand-copied `#[repr(C)]` structs handed to the
driver through raw `p_next` chains. Nothing in the type system relates them to the C
definitions any more, so an edit that inserts, drops, widens or re-pads a field is not a
compile error — it is the driver reading our bytes at the wrong offsets, silently. The
sibling vendored ABI in `amf.rs` has carried assertions for exactly this reason; these two
had none at all.
Adds size, alignment and per-field offset assertions for all 19 vendored structs. They are
`const` rather than `#[cfg(test)]` (the shape `amf.rs` uses) so they hold in every build
including the shipped one, and on any target the modules compile for.
Assertions cannot catch a swap of two same-typed fields — the offsets are unchanged — so
the field order was diffed field-by-field against the authoritative headers while writing
them: `vulkan_core.h` and `vk_video/vulkan_video_codec_av1std_encode.h` from Vulkan-Headers
`main` as of 2026-07-25. That diff covered every struct, every `ST_*` structure-type value,
every flag bit and both enum groups, and found no drift — the vendored copies are faithful.
The one remaining hand-copied table the compiler still cannot see is the bitfield member
order inside the three `*Flags` words, where a wrong index means the driver reads
`use_superres` where we meant `render_and_frame_size_different`. Three tests pin those to
the header by listing the members in C declaration order and asserting the Nth setter
writes bit N, with the trailing `reserved` field checked too — a dropped member shifts
`reserved` down and fails.
Verified with the canonical Linux gate (docker linux/amd64): fmt, clippy `--all-targets`
default and `nvenc,vulkan-encode,pyrowave`, and both test legs.
enricobuehler
a17413327b