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/vendor/pyrowave/shaders/slangmosh.json

@@ -0,0 +1,71 @@
+{
+	"shaders": [
+		{
+			"name": "dwt",
+			"compute": true,
+			"path": "dwt.comp",
+			"variants": [
+				{ "define": "PRECISION", "count": 3, "resolve": false },
+				{ "define": "FP16", "count": 2, "resolve": true }
+			]
+		},
+		{
+			"name": "block_packing",
+			"compute": true,
+			"path": "block_packing.comp"
+		},
+		{
+			"name": "idwt",
+			"compute": true,
+			"path": "idwt.comp",
+			"variants": [
+				{ "define": "PRECISION", "count": 3, "resolve": false },
+				{ "define": "FP16", "count": 2, "resolve": true }
+			]
+		},
+		{
+			"name": "idwt_vs",
+			"path": "idwt.vert"
+		},
+		{
+			"name": "idwt_fs",
+			"path": "idwt.frag",
+			"variants": [
+				{ "define": "CHROMA_CONFIG", "count": 3 }
+			]
+		},
+		{
+			"name": "power_to_db",
+			"compute": true,
+			"path": "power_to_db.comp"
+		},
+		{
+			"name": "analyze_rate_control",
+			"compute": true,
+			"path": "analyze_rate_control.comp"
+		},
+		{
+			"name": "analyze_rate_control_finalize",
+			"compute": true,
+			"path": "analyze_rate_control_finalize.comp"
+		},
+		{
+			"name": "resolve_rate_control",
+			"compute": true,
+			"path": "resolve_rate_control.comp"
+		},
+		{
+			"name": "wavelet_quant",
+			"compute": true,
+			"path": "wavelet_quant.comp"
+		},
+		{
+			"name": "wavelet_dequant",
+			"compute": true,
+			"path": "wavelet_dequant.comp",
+			"variants": [
+				{ "define": "STORAGE_MODE", "count" : 3 }
+			]
+		}
+	]
+}