feat(host): PyroWave encoder — Phase 1 of the LAN low-latency codec plan

PyroWaveEncoder behind --features pyrowave + an explicit
PUNKTFUNK_ENCODER=pyrowave (loud EXPERIMENTAL warning: no client can
decode the stream until CODEC_PYROWAVE negotiation lands, plan Phase 2).

Design (plan §4.3): a private ash Vulkan-1.3 device shared with pyrowave
via pyrowave_create_device — DeviceHold pins the instance/device
create-infos the 0.4.0 API requires alive for the device's lifetime.
Capture dmabufs pass straight through on ANY vendor
(linux_zero_copy_is_vaapi → true for pyrowave; NVIDIA dmabuf→Vulkan
import validated by upstream's interop test on .21) with the same
per-buffer import cache as the Vulkan Video backend; the shared
rgb2yuv.comp BT.709-limited CSC writes R8+RG8 images pyrowave samples
directly (R/G view swizzles synthesize Cb/Cr — no NV12 copy). Encode
records into OUR command buffer (pyrowave_device_set_command_buffer), so
ingest + CSC + encode are one submission with a sub-ms fence wait; the
AU is exactly one pyrowave packet, keyframe=true on every frame.
reconfigure_bitrate is a free in-place budget change (Phase 3 pins the
session rate); reset() recreates only the pyrowave encoder object.

Shared ash leaf helpers (dmabuf import, image/memory utils) extracted
from vulkan_video.rs into encode/linux/vk_util.rs — vulkan-encode
builds unchanged.

Validated on .21 (RTX 5070 Ti): pyrowave_smoke green — encodes CPU
fills through the full open→CSC→GPU-encode→packetize path, decodes
every AU with upstream's own decoder, checks BT.709 plane means ±3;
rate retarget + rebuild covered. clippy clean, 308 host tests green
with the feature on.

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

Cargo.lock

@@ -3120,6 +3120,7 @@ dependencies = [
  "pf-driver-proto",
  "pipewire",
  "punktfunk-core",
+ "pyrowave-sys",
  "quinn",
  "rand 0.8.6",
  "rcgen",