feat(apple): PyroWave Phase 5 — native Metal decode on Mac / Apple TV / iPad (§4.7)

The Apple client now decodes PyroWave natively on the presenter's own MTLDevice —
no MoltenVK, no upstream C++ in the app. Completes and wires up the decoder whose
early working-tree snapshot rode along in 9127c346:

- MetalWaveletShaders.swift: wavelet_dequant + idwt hand-ported from the vendored
  GLSL (STORAGE_MODE 0 only; subgroup scans → 32-wide simdgroups; DCShift spec
  constant → function constant; precision-1 split: fp16 levels 0-1 / fp32 2-4).
- MetalWaveletDecoder.swift: Swift reimplementation of push_packet/decode_packet
  incl. the Phase-4 chunk-aligned window walk (FRAG chains, zeroed missing shards,
  the >half-blocks partial rule), init_block_meta's block-index space, and the
  42-dequant + 13-idwt dispatch structure with encoder-boundary barriers. SOF-dims
  changes rebuild the size-dependent resources, which is also the mid-stream
  resize path. Ring of 4 output plane sets on the presenter's queue.
- Presenter: pf_frag_planar (3xR8, the planar_csc.frag twin) + renderPlanar with
  a shared present tail; ReadyFrame carries an image enum (.video | .planar).
- Stage2Pipeline: a dedicated PyroWave pump — no VideoToolbox machinery, no
  keyframe/re-anchor recovery (all-intra; partials render as localized blur by
  design), newest-frame-index staleness guard for late partials.
- Opt-in: "PyroWave (wired LAN)" codec entry (probe-gated, ≈A13 floor via a real
  kernel-compile probe), selecting it advertises + prefers the codec and forces
  the session SDR (HDR/10-bit/4:4:4 caps dropped, plan contract).
- Core ABI: punktfunk_connection_shard_payload() — the Welcome's negotiated shard
  payload, needed by native decoders to walk chunk-aligned AUs.
- Validation: golden fixtures generated by the host encoder + upstream's own
  decoder (pyrowave_dump_golden, RTX 5070 Ti); the Metal decode PSNR-matches at
  77-88 dB across all planes for dense AND chunk-aligned AUs, and a hole-punched
  partial still decodes. Parser unit tests cover the window walk, FRAG chains,
  broken chains, the half-blocks gate, and the block-index layout.

Tests: apple 134 green (mac; iOS/tvOS build), host 312 w/ pyrowave on .21,
core 148 w/ quic; clippy/fmt clean.

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

clients/apple/Tests/PunktfunkKitTests/AV1Tests.swift

@@ -237,10 +237,11 @@ final class AV1Tests: XCTestCase {
         let ready = try XCTUnwrap(frame)
         XCTAssertEqual(ready.ptsNs, 42_000_000)
         XCTAssertFalse(ready.isHDR)
-        XCTAssertEqual(CVPixelBufferGetWidth(ready.pixelBuffer), 320)
-        XCTAssertEqual(CVPixelBufferGetHeight(ready.pixelBuffer), 180)
+        let buffer = try XCTUnwrap(ready.pixelBuffer, "a VT decode delivers a .video frame")
+        XCTAssertEqual(CVPixelBufferGetWidth(buffer), 320)
+        XCTAssertEqual(CVPixelBufferGetHeight(buffer), 180)
         XCTAssertEqual(
-            CVPixelBufferGetPixelFormatType(ready.pixelBuffer),
+            CVPixelBufferGetPixelFormatType(buffer),
             kCVPixelFormatType_420YpCbCr8BiPlanarVideoRange, "SDR AV1 must decode to NV12")
         decoder.reset()
     }