feat(host): vendor PyroWave + minimal Granite subset as crates/pyrowave-sys

Phase 0 of design/pyrowave-codec-plan.md — the opt-in wired-LAN ultra-low-
latency codec. Vendored at upstream 509e4f88 (API 0.4.0, Granite 44362775,
volk + vulkan-headers pins in PUNKTFUNK-VENDOR.txt), pruned to the 6.6 MB
the standalone no-renderer build needs; scripts/vendor-pyrowave.sh
reproduces the tree (a pin bump is protocol-affecting, plan §4.2).

build.rs drives the wrapper CMakeLists (static archives incl. a static
C-API lib upstream only ships shared) + bindgen over pyrowave.h; Linux and
Windows only, empty stub elsewhere (Apple gets a native Metal port, §4.7).
Offline-safe by construction: no network, no system lib, vendored Vulkan
headers — same model as the opus dep (flatpak builder has no network).

Phase-0 validation on .21 (RTX 5070 Ti, driver 610.43.03):
- upstream pyrowave-c-test + interop test (incl. dmabuf/DRM-modifier
  Vulkan<->Vulkan) pass, from the pristine AND the pruned tree
- GPU kernel times at ~1.6 bpp noise: encode/decode 0.090/0.042 ms @800p,
  0.146/0.067 @1080p, 0.226/0.103 @1440p, 0.477/0.201 @4K — order of
  magnitude under NVENC's 1-2 ms retrieve, CBR lands within ~100 B of
  target
- cargo test -p pyrowave-sys green (static link + API-version pin check)

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

crates/pyrowave-sys/CMakeLists.txt

@@ -0,0 +1,30 @@
+cmake_minimum_required(VERSION 3.20)
+project(pyrowave-sys LANGUAGES CXX C)
+
+if(NOT DEFINED PYROWAVE_VENDOR_DIR)
+    set(PYROWAVE_VENDOR_DIR ${CMAKE_CURRENT_SOURCE_DIR}/vendor/pyrowave)
+endif()
+
+# Mirror upstream pyrowave's standalone (top-level) Granite configuration
+# (CMakeLists.txt lines 88-99 at the vendored pin), but produce static
+# archives only — the Rust crate links the C API statically.
+set(GRANITE_RENDERER OFF CACHE BOOL "" FORCE)
+set(GRANITE_VULKAN_SPIRV_CROSS OFF CACHE BOOL "" FORCE)
+set(GRANITE_VULKAN_SHADER_MANAGER_RUNTIME_COMPILER OFF CACHE BOOL "" FORCE)
+set(GRANITE_VULKAN_SYSTEM_HANDLES OFF CACHE BOOL "" FORCE)
+set(GRANITE_SHADER_COMPILER_OPTIMIZE OFF CACHE BOOL "" FORCE)
+set(GRANITE_POSITION_INDEPENDENT ON CACHE BOOL "" FORCE)
+set(GRANITE_VULKAN_FOSSILIZE OFF CACHE BOOL "" FORCE)
+set(GRANITE_SHIPPING ON CACHE BOOL "" FORCE)
+set(GRANITE_PLATFORM "null" CACHE STRING "" FORCE)
+
+add_subdirectory(${PYROWAVE_VENDOR_DIR}/Granite ${CMAKE_CURRENT_BINARY_DIR}/Granite EXCLUDE_FROM_ALL)
+# Not top-level from here, so upstream's CMake only defines the static
+# `pyrowave` codec library (shared lib / tests / install rules are skipped).
+add_subdirectory(${PYROWAVE_VENDOR_DIR} ${CMAKE_CURRENT_BINARY_DIR}/pyrowave EXCLUDE_FROM_ALL)
+
+# The C API as a static archive. Upstream only ships it as a SHARED target;
+# compiling pyrowave_c.cpp against the same deps is equivalent minus the
+# dllexport attributes (PYROWAVE_EXPORT_SYMBOLS stays undefined).
+add_library(pyrowave-capi STATIC ${PYROWAVE_VENDOR_DIR}/pyrowave_c.cpp)
+target_link_libraries(pyrowave-capi PRIVATE pyrowave granite-vulkan)