fix(pyrowave): per-session raw-dmabuf zero-copy capture on the Linux NVIDIA host

A PyroWave session on an NVIDIA-auto host was forced onto CPU-RGB capture
(session_plan flipped gpu=false): Mutter blits tiled->LINEAR, we mmap +
de-pad ~30 MB, the encoder re-uploads it - three full-frame CPU touches
per frame at 5120x1440 while an HEVC session on the same box rides the
tiled EGL/CUDA zero-copy. The dmabuf passthrough + Vulkan tiled import
were already validated (8dc5d672) but only reachable via the global
PUNKTFUNK_ENCODER=pyrowave lab policy.

ZeroCopyPolicy gains pyrowave_session (from OutputFormat.pyrowave, i.e.
the negotiated codec): the capturer skips the NVENC-only EGL->CUDA
importer, takes the raw-dmabuf passthrough, and advertises the wavelet
encoder's Vulkan-importable modifiers so Mutter+NVIDIA negotiates tiled
zero-copy. The forced-CPU flip in session_plan is gone.

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

crates/pf-capture/src/lib.rs

@@ -244,8 +244,13 @@ pub struct ZeroCopyPolicy {
     /// The resolved backend produces GPU-resident frames (everything but the software encoder) —
     /// used only to phrase the CPU-fallback warning (the host `encode::resolved_backend_is_gpu`).
     pub backend_is_gpu: bool,
+    /// THIS session encodes PyroWave: the frames' consumer is the wavelet encoder's own Vulkan
+    /// device, which imports raw dmabufs on ANY vendor — so the capturer takes the raw-dmabuf
+    /// passthrough (like the VAAPI backend) instead of the EGL→CUDA import whose payloads only
+    /// NVENC can consume. Per-session (the codec is negotiated), unlike `backend_is_vaapi`.
+    pub pyrowave_session: bool,
     /// The PyroWave encoder's Vulkan-importable dmabuf modifiers for the capture's packed-RGB fourcc,
-    /// resolved when the encoder pref is `pyrowave` (the passthrough advertises them so Mutter+NVIDIA,
+    /// resolved when the session encodes PyroWave (the passthrough advertises them so Mutter+NVIDIA,
     /// which allocates tiled-only, still negotiates zero-copy). Empty otherwise.
     pub pyrowave_modifiers: Vec<u64>,
 }