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/Granite/filesystem/netfs/fs-netfs.hpp

@@ -0,0 +1,92 @@
+/* Copyright (c) 2017-2026 Hans-Kristian Arntzen
+ *
+ * Permission is hereby granted, free of charge, to any person obtaining
+ * a copy of this software and associated documentation files (the
+ * "Software"), to deal in the Software without restriction, including
+ * without limitation the rights to use, copy, modify, merge, publish,
+ * distribute, sublicense, and/or sell copies of the Software, and to
+ * permit persons to whom the Software is furnished to do so, subject to
+ * the following conditions:
+ *
+ * The above copyright notice and this permission notice shall be
+ * included in all copies or substantial portions of the Software.
+ *
+ * THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND,
+ * EXPRESS OR IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF
+ * MERCHANTABILITY, FITNESS FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT.
+ * IN NO EVENT SHALL THE AUTHORS OR COPYRIGHT HOLDERS BE LIABLE FOR ANY
+ * CLAIM, DAMAGES OR OTHER LIABILITY, WHETHER IN AN ACTION OF CONTRACT,
+ * TORT OR OTHERWISE, ARISING FROM, OUT OF OR IN CONNECTION WITH THE
+ * SOFTWARE OR THE USE OR OTHER DEALINGS IN THE SOFTWARE.
+ */
+
+#pragma once
+#include "fs-netfs.hpp"
+#include "network.hpp"
+#include "../filesystem.hpp"
+#include "netfs.hpp"
+#include <unordered_map>
+#include <future>
+#include <thread>
+
+namespace Granite
+{
+struct FSReader;
+class NetworkFile : public File
+{
+public:
+	static NetworkFile *open(Looper &looper, const std::string &path, FileMode mode);
+	~NetworkFile();
+	void *map() override;
+	void *map_write(size_t size) override;
+	void unmap() override;
+	size_t get_size() override;
+	bool reopen() override;
+
+private:
+	NetworkFile() = default;
+	bool init(Looper &looper, const std::string &path, FileMode mode);
+	std::string path;
+	FileMode mode;
+	Looper *looper = nullptr;
+	std::future<std::vector<uint8_t>> future;
+	std::vector<uint8_t> buffer;
+	bool has_buffer = false;
+	bool need_flush = false;
+};
+
+struct FSNotifyCommand;
+class NetworkFilesystem : public FilesystemBackend
+{
+public:
+	NetworkFilesystem();
+	~NetworkFilesystem();
+	std::vector<ListEntry> list(const std::string &path) override;
+	std::unique_ptr<File> open(const std::string &path, FileMode mode) override;
+	bool stat(const std::string &path, FileStat &stat) override;
+
+	FileNotifyHandle install_notification(const std::string &path, std::function<void (const FileNotifyInfo &)> func) override;
+
+	void uninstall_notification(FileNotifyHandle handle) override;
+
+	void poll_notifications() override;
+
+	int get_notification_fd() const override
+	{
+		return -1;
+	}
+
+private:
+	std::thread looper_thread;
+	Looper looper;
+	void looper_entry();
+	FSNotifyCommand *notify = nullptr;
+
+	std::unordered_map<FileNotifyHandle, std::function<void (const FileNotifyInfo &)>> handlers;
+	std::mutex lock;
+	std::vector<FileNotifyInfo> pending;
+
+	void setup_notification();
+	void signal_notification(const FileNotifyInfo &info);
+};
+}