feat(encode): native QSV backend — libvpl-sys + qsv.rs (Phases 0-3 of design/native-qsv-encoder.md)

Vendored MIT VPL dispatcher (static, trimmed tree, pin 674d015b/v2.17.0) built
via cmake+bindgen behind new feature 'qsv' (pf-encode + punktfunk-host forward).
qsv.rs: dispatcher session on the capture adapter (LUID-matched), SetHandle
D3D11, AsyncDepth=1/GopRefDist=1/VDEnc/CBR + HRD-off low-latency config,
GetSurfaceForEncode + GPU CopySubresourceRegion input (zero-copy, no readback
path), bounded sync-point poll, in-place reset with teardown escalation, no-IDR
bitrate retarget (Reset + StartNewSequence=OFF), 10-bit P010 HEVC-Main10/AV1,
HDR mastering/CLL SEI-OBU at IDR + BT.2020/PQ VSI, LTR-RFI via mfxExtRefListCtrl
(AMF slot policy port, Query-gated per codec, wire-index FrameOrder pinning).
Dispatch: native-first with ffmpeg fallback + PUNKTFUNK_QSV_FFMPEG hatch;
probes (can_encode_10bit / windows_codec_support / windows_backend_is_probed)
now answer natively for QSV.

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

crates/libvpl-sys/vendor/libvpl/api/CMakeLists.txt

@@ -0,0 +1,41 @@
+# ##############################################################################
+# Copyright (C) Intel Corporation
+#
+# SPDX-License-Identifier: MIT
+# ##############################################################################
+
+cmake_minimum_required(VERSION 3.13.0)
+
+set(VPL_API_INCLUDE_DIR ${CMAKE_CURRENT_SOURCE_DIR})
+
+if(DEFINED ENV{ONEVPL_API_HEADER_DIRECTORY})
+  set(VPL_API_INCLUDE_DIR $ENV{ONEVPL_API_HEADER_DIRECTORY})
+  message(STATUS "Using custom API header directory: ${VPL_API_INCLUDE_DIR}")
+endif()
+
+# get API version
+file(READ ${VPL_API_INCLUDE_DIR}/vpl/mfxdefs.h mfxdefs)
+
+string(REGEX MATCH "MFX_VERSION_MAJOR ([0-9]*)" _ ${mfxdefs})
+set(API_VERSION_MAJOR ${CMAKE_MATCH_1})
+set(API_VERSION_MAJOR
+    ${API_VERSION_MAJOR}
+    PARENT_SCOPE)
+
+string(REGEX MATCH "MFX_VERSION_MINOR ([0-9]*)" _ ${mfxdefs})
+set(API_VERSION_MINOR ${CMAKE_MATCH_1})
+set(API_VERSION_MINOR
+    ${API_VERSION_MINOR}
+    PARENT_SCOPE)
+
+message(STATUS "API version: ${API_VERSION_MAJOR}.${API_VERSION_MINOR}")
+add_library(vpl-api INTERFACE)
+
+target_include_directories(vpl-api INTERFACE ${VPL_API_INCLUDE_DIR})
+
+if(INSTALL_DEV)
+  install(
+    DIRECTORY ${VPL_API_INCLUDE_DIR}/vpl
+    DESTINATION ${CMAKE_INSTALL_INCLUDEDIR}
+    COMPONENT ${VPL_COMPONENT_DEV})
+endif()