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/Sources/PunktfunkKit/Video/AnnexB.swift

@@ -26,12 +26,18 @@ public enum VideoCodec: Equatable {
     case h264
     case hevc
     case av1
+    /// PyroWave wavelet (opt-in wired-LAN low-latency codec): not a NAL/OBU codec and not
+    /// VideoToolbox-decoded at all — the Metal wavelet decoder consumes the raw AUs
+    /// (Stage2Pipeline's PyroWave pump). Only ever resolved when this client both advertised
+    /// and preferred it.
+    case pyrowave
 
     /// Resolve from the wire `Welcome.codec` byte (`PUNKTFUNK_CODEC_*`; unknown → HEVC).
     public init(wire: UInt8) {
         switch wire {
         case 0x01: self = .h264 // PUNKTFUNK_CODEC_H264
         case 0x04: self = .av1 // PUNKTFUNK_CODEC_AV1
+        case 0x08: self = .pyrowave // PUNKTFUNK_CODEC_PYROWAVE
         default: self = .hevc // PUNKTFUNK_CODEC_HEVC — the default / older-host codec
         }
     }
@@ -147,8 +153,8 @@ public enum AnnexB {
             sets = [vps, sps, pps]
         case .h264:
             sets = [sps, pps]
-        case .av1:
-            return nil // OBU stream, no parameter-set NALs — handled in AV1.swift, never here
+        case .av1, .pyrowave:
+            return nil // no parameter-set NALs — dispatched in AV1.swift, never reaches here
         }
 
         var format: CMVideoFormatDescription?
@@ -184,8 +190,8 @@ public enum AnnexB {
                     parameterSetSizes: sizes,
                     nalUnitHeaderLength: 4,
                     formatDescriptionOut: &format)
-            case .av1:
-                break // unreachable — the .av1 arm above already returned
+            case .av1, .pyrowave:
+                break // unreachable — the arm above already returned
             }
         }
         return status == noErr ? format : nil