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/shaders/planar_csc.frag

@@ -0,0 +1,84 @@
+// Planar 3-plane YCbCr → RGBA — the PyroWave variant of nv12_csc.frag (separate Cb and
+// Cr R8 planes instead of an interleaved CbCr plane; design/pyrowave-codec-plan.md §4.5).
+// Same push-constant contract (csc_rows precomputes the matrix + range expansion), same
+// output modes — though PyroWave itself is 8-bit SDR BT.709 limited, keeping parity means
+// one less divergence if the codec ever signals more. 4:4:4 needs no shader change: the
+// chroma planes arrive full-res and the siting correction self-disables.
+//
+// Regenerate: shaders/build.sh (committed .spv, no build-time toolchain).
+#version 450
+
+layout(location = 0) in vec2 v_uv;
+layout(location = 0) out vec4 frag;
+
+layout(set = 0, binding = 0) uniform sampler2D u_y;
+layout(set = 0, binding = 1) uniform sampler2D u_cb;
+layout(set = 0, binding = 2) uniform sampler2D u_cr;
+
+layout(push_constant) uniform Csc {
+    vec4 r0;
+    vec4 r1;
+    vec4 r2;
+    vec4 params; // x: mode, y: tonemap peak, z/w: reserved
+} pc;
+
+// SMPTE ST.2084 (PQ) EOTF: code value → display-referred linear, normalized to 1.0 =
+// 10000 nits.
+vec3 pq_eotf(vec3 e) {
+    const float m1 = 0.1593017578125;  // 2610/16384
+    const float m2 = 78.84375;         // 2523/4096 * 128
+    const float c1 = 0.8359375;        // 3424/4096
+    const float c2 = 18.8515625;       // 2413/4096 * 32
+    const float c3 = 18.6875;          // 2392/4096 * 32
+    vec3 p = pow(max(e, vec3(0.0)), vec3(1.0 / m2));
+    return pow(max(p - c1, vec3(0.0)) / (c2 - c3 * p), vec3(1.0 / m1));
+}
+
+// BT.2020 → BT.709 primaries (linear light).
+vec3 bt2020_to_709(vec3 c) {
+    return mat3(
+         1.6605, -0.1246, -0.0182,
+        -0.5876,  1.1329, -0.1006,
+        -0.0728, -0.0083,  1.1187
+    ) * c;
+}
+
+// Linear → sRGB OETF.
+vec3 srgb_oetf(vec3 c) {
+    c = clamp(c, 0.0, 1.0);
+    bvec3 lo = lessThanEqual(c, vec3(0.0031308));
+    vec3 hi = 1.055 * pow(c, vec3(1.0 / 2.4)) - 0.055;
+    return mix(hi, c * 12.92, vec3(lo));
+}
+
+void main() {
+    // Left-cosited 4:2:0 chroma sampled at luma UV assumes CENTER siting — offset +0.25
+    // chroma texels to re-align (same correction as nv12_csc.frag; self-disables when the
+    // chroma plane is full-res).
+    vec2 cuv = v_uv;
+    int cw = textureSize(u_cb, 0).x;
+    if (cw < textureSize(u_y, 0).x) {
+        cuv.x += 0.25 / float(cw);
+    }
+    vec3 yuv = vec3(texture(u_y, v_uv).r, texture(u_cb, cuv).r, texture(u_cr, cuv).r);
+    vec3 rgb = vec3(
+        dot(pc.r0.xyz, yuv) + pc.r0.w,
+        dot(pc.r1.xyz, yuv) + pc.r1.w,
+        dot(pc.r2.xyz, yuv) + pc.r2.w
+    );
+
+    if (pc.params.x > 0.5) {
+        vec3 lin = pq_eotf(clamp(rgb, 0.0, 1.0)) * (10000.0 / 203.0);
+        lin = max(bt2020_to_709(lin), vec3(0.0));
+        float peak = max(pc.params.y, 1.0001);
+        float l = max(lin.r, max(lin.g, lin.b));
+        if (l > 1.0) {
+            float mapped = 1.0 + (l - 1.0) / (1.0 + (l - 1.0) / (peak - 1.0));
+            lin *= mapped / l;
+        }
+        rgb = srgb_oetf(lin);
+    } else {
+        rgb = clamp(rgb, 0.0, 1.0);
+    }
+    frag = vec4(rgb, 1.0);
+}