feat(video): HDR10/P010 end to end (phase 6)

The client now advertises VIDEO_CAP_10BIT|HDR and carries the result all
the way to glass:

- csc_rows is bit-depth exact (10-bit limited code points differ from
  8-bit by ~half a code) and folds in the P010/X6 MSB-packing factor;
  new 10-bit white/black tests.
- The CSC shader grows a params block: mode 0 passes the transfer
  through (SDR as-is, or PQ onto an HDR10 swapchain); mode 1 tonemaps
  PQ→SDR in-shader (ST.2084 EOTF, 203-nit reference white exposure,
  BT.2020→709, soft maxRGB rolloff, sRGB encode) for desktops without
  an HDR surface. PUNKTFUNK_TONEMAP_PEAK tunes the rolloff.
- The presenter probes VK_EXT_swapchain_colorspace + an HDR10/ST.2084
  10-bit surface format and flips modes in-band with the stream's PQ
  signaling: fence-quiesce, then CSC pass + video image (10-bit
  A2B10G10R10 intermediate — PQ in 8 bits bands) + overlay pipe +
  swapchain rebuild through the deferred-destroy rules.
- P010 decodes through all three paths: Vulkan Video (X6 multiplanar
  pool, R10X6 plane views), VAAPI dmabuf (R16/RG1616 plane imports),
  software (swscale as before).
- session pump advertises the caps; the host still gates Main10 behind
  its PUNKTFUNK_10BIT policy.

Probed on glass hardware: the KDE/NVIDIA surface exposes
A2B10G10R10+HDR10_ST2084, so true PQ passthrough is available there.
Known v1 gaps: software-decode PQ shows untonemapped (8-bit RGBA
carries the transfer baked); the SDR overlay composites unscaled onto
an HDR10 surface (dim OSD); no vkSetHdrMetadataEXT yet.

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

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

@@ -211,7 +211,11 @@ fn pump(
         params.compositor,
         params.gamepad,
         params.bitrate_kbps,
-        0, // video_caps: the Linux client has no 10-bit/HDR present path yet
+        // 10-bit Main10 + PQ HDR10: the Vulkan presenter decodes P010 (Vulkan
+        // Video/VAAPI/software) and presents PQ on an HDR10 swapchain where the desktop
+        // offers one, tonemapping in the CSC shader where it doesn't. The host still
+        // gates the upgrade behind its own PUNKTFUNK_10BIT policy.
+        punktfunk_core::quic::VIDEO_CAP_10BIT | punktfunk_core::quic::VIDEO_CAP_HDR,
         params.audio_channels,
         crate::video::decodable_codecs(), // codecs FFmpeg can decode (HEVC/H.264/AV1)
         params.preferred_codec,           // the user's soft codec preference (0 = auto)

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

@@ -1063,8 +1063,10 @@ impl VulkanDecoder {
             }
             let fc = (*hwfc_ref).data as *mut ffi::AVHWFramesContext;
             let sw = (*fc).sw_format;
-            if sw != ffi::AVPixelFormat::AV_PIX_FMT_NV12 {
-                bail!("Vulkan decode output {sw:?} unsupported (NV12 only for now)");
+            if sw != ffi::AVPixelFormat::AV_PIX_FMT_NV12
+                && sw != ffi::AVPixelFormat::AV_PIX_FMT_P010LE
+            {
+                bail!("Vulkan decode output {sw:?} unsupported (NV12/P010 only)");
             }
             let vkfc = (*fc).hwctx as *const pf_ffvk::AVVulkanFramesContext;
             let vk_format = (*vkfc).format[0] as i32;