feat(video): Vulkan Video decode on the presenter's device (NVIDIA hw decode)

FFmpeg's Vulkan Video decoder now runs on the PRESENTER's own VkDevice —
the decoded VkImage feeds the existing CICP CSC pass directly: zero
copy, no interop, and NVIDIA gets hardware decode for the first time
(its VAAPI is unusable by design). One decode architecture for every
vendor going forward; VAAPI-dmabuf and software remain the fallbacks
(auto: vulkan → vaapi → software; PUNKTFUNK_DECODER=vulkan pins it).

Presenter: instance 1.3; probes VK_KHR_video_queue/decode_queue + codec
extensions, a VIDEO_DECODE queue family (+ its codec caps via
QueueFamilyVideoPropertiesKHR), and the samplerYcbcrConversion/
timelineSemaphore/synchronization2 features — all enabled at device
creation when present, exported as a VulkanDecodeDevice handle bundle.

Decoder: AVVulkanDeviceContext built over those handles via pf-ffvk
(features chain, extension lists, deprecated queue indices + the qf[]
map); get_format supplies OUR frames context with MUTABLE_FORMAT so the
presenter's per-plane views are legal; output is DecodedImage::VkFrame
carrying AVVkFrame/frames-ctx pointers plus the lock fns.

Present: R8+R8G8 plane views over the multiplanar image, the live sync
state read under the AVVulkanFramesContext lock, a timeline-semaphore
wait(sem_value)/signal(sem_value+1) folded into the submit, layout/
queue-family/sem_value written back per FFmpeg's contract, and the frame
guard parked in the retire queue until the fence. CSC pass + video
framebuffer are now unconditional (NVIDIA has no dmabuf-import path).

Verified on the RTX 5070 Ti: device creates with decode_qf=3,
caps=DECODE_H264|H265|AV1|VP9; swapchain unaffected. Live stream
validation next.

Co-Authored-By: Claude Fable 5 <noreply@anthropic.com>

crates/pf-client-core/src/session.rs

@@ -35,6 +35,9 @@ pub struct SessionParams {
     /// Library id for the host to launch this session (`"steam:570"`, from the library
     /// page); `None` = plain desktop session.
     pub launch: Option<String>,
+    /// The presenter's shared Vulkan device, when its stack can run FFmpeg's Vulkan
+    /// Video decoder (decode lands as VkImages the presenter samples directly).
+    pub vulkan: Option<crate::video::VulkanDecodeDevice>,
     /// Pinned host fingerprint; `None` = trust on first use (caller persists the observed one).
     pub pin: Option<[u8; 32]>,
     pub identity: (String, String),
@@ -241,7 +244,7 @@ fn pump(
         welcome_codec = connector.codec,
         "negotiated video codec"
     );
-    let mut decoder = match Decoder::new(codec_id, &params.decoder) {
+    let mut decoder = match Decoder::new(codec_id, &params.decoder, params.vulkan.as_ref()) {
         Ok(d) => d,
         Err(e) => {
             let _ = ev_tx.send_blocking(SessionEvent::Ended(Some(format!("video decoder: {e}"))));
@@ -314,11 +317,13 @@ fn pump(
                         dec_path = match &image {
                             DecodedImage::Cpu(_) => "software",
                             DecodedImage::Dmabuf(_) => "vaapi",
+                            DecodedImage::VkFrame(_) => "vulkan",
                         };
                         if total_frames == 1 {
                             let (w, h, path) = match &image {
                                 DecodedImage::Cpu(c) => (c.width, c.height, "software"),
                                 DecodedImage::Dmabuf(d) => (d.width, d.height, "vaapi-dmabuf"),
+                                DecodedImage::VkFrame(v) => (v.width, v.height, "vulkan-video"),
                             };
                             tracing::info!(width = w, height = h, path, "first frame decoded");
                         }