feat(client): PyroWave planar present path + Linux NVENC match-arm fix (Phase 2b, part 2)

The arch package job (--features nvenc) tripped the same class of
Codec::PyroWave non-exhaustive matches as windows-host had, in
nvenc_cuda.rs (6 sites) — dispatch-guarded unreachable!() arms, plus
the vk_util-extraction leftover unused imports in vulkan_video.rs.
All Linux host feature combos (none / pyrowave / nvenc,vulkan-encode /
all three) now compile clean on .21.

Presenter: planar_csc.frag (+ committed .spv) — the 3-plane variant of
nv12_csc.frag (separate Cb/Cr R8 planes, same push-constant CSC-row
contract, siting correction self-disables at full-res chroma).
CscPass grows a shared builder + new_planar()/bind_planes_planar()
(GENERAL-layout descriptors — pyrowave planes stay GENERAL); the Vk
presenter builds the planar pass when the device passed the pyrowave
probe, FrameInput::PyroWave rides present_frame (no acquire barrier
needed: the decoder fence-completed and barriered the planes on the
same queue), and run.rs presents it with no demote rung (only device
loss ends the session).

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

crates/pf-presenter/Cargo.toml

@@ -43,3 +43,8 @@ windows-sys = { version = "0.61", features = [
     "Win32_UI_Shell",
     "Win32_UI_WindowsAndMessaging",
 ] }
+
+[features]
+# PyroWave planar present path (the wired-LAN wavelet codec) — forwards to the decode
+# backend in pf-client-core; OFF by default.
+pyrowave = ["pf-client-core/pyrowave"]