refactor(host/W6.2): extract the video encode backends into the pf-encode crate

encode.rs + encode/* (NVENC, VAAPI, native AMF, AMF/QSV ffmpeg, direct-SDK
NVENC/CUDA, raw Vulkan-Video, PyroWave, openh264) move into crates/pf-encode
behind one Encoder trait + open_video selector (plan §W6). The crate speaks the
shared frame vocabulary (pf-frame: CapturedFrame/PixelFormat + the DXGI identity
D3d11Frame/make_device) and pf-zerocopy (CUDA context/buffers), and NEVER
pf-capture — the capture→encode edge is one-way (ZeroCopyPolicy, prior commit).

Dep moves: the heavy encoder deps (ffmpeg-next, the NVENC SDK, openh264,
pyrowave-sys) move from the host to pf-encode; the host's
nvenc/amf-qsv/vulkan-encode/pyrowave features now FORWARD to pf-encode/*. The
host keeps a mod-encode shim (pub use pf_encode) so every crate::encode::* path
(negotiator + GameStream/native/mgmt planes) is unchanged.

resolve_render_adapter_luid moves from the host's windows/win_adapter.rs into
pf-gpu (both pf-encode and pf-capture need it as a peer of GPU selection); its 5
call sites (encode amf/nvenc, capture idd_push/synthetic_nv12, vdisplay manager)
rewire to pf_gpu::resolve_render_adapter_luid and win_adapter.rs is deleted.
pf-frame's make_device gains a # Safety section (public-unsafe-fn lint, latent
since the pf-frame carve — a full-workspace -D warnings clippy catches it).

Verified: Linux clippy -D warnings (pf-encode + host nvenc,vulkan-encode,pyrowave
--all-targets) + 13/13 pf-encode + 299/299 host tests; Windows clippy -D warnings
(pf-encode nvenc,amf-qsv --all-targets + host nvenc,amf-qsv --all-targets)
Finished exit 0.

Co-Authored-By: Claude Opus 4.8 (1M context) <noreply@anthropic.com>

crates/pf-frame/src/dxgi.rs

@@ -55,6 +55,11 @@ pub fn pack_luid(luid: LUID) -> i64 {
 /// adapter). Used at open and on every ACCESS_LOST: a device created on one desktop cannot sustain a
 /// duplication on a *different* desktop (perpetual ACCESS_LOST), so the secure-desktop switch needs a
 /// device made while the thread is attached to that desktop.
+///
+/// # Safety
+/// `adapter` must be a live `IDXGIAdapter1` for the duration of the call. The fn calls the D3D11 /
+/// DXGI FFI (`D3D11CreateDevice`, GPU scheduling-priority hardening) but forms no lasting alias to
+/// `adapter`; the returned device/context are the sole owners of the new COM objects.
 pub unsafe fn make_device(adapter: &IDXGIAdapter1) -> Result<(ID3D11Device, ID3D11DeviceContext)> {
     let mut device: Option<ID3D11Device> = None;
     let mut context: Option<ID3D11DeviceContext> = None;