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/Connection/PunktfunkConnection.swift

@@ -337,9 +337,15 @@ public final class PunktfunkConnection {
     public private(set) var resolvedAudioChannels: UInt8 = 2
 
     /// The video codec the host resolved for this session (`Welcome.codec`, `PUNKTFUNK_CODEC_*`):
-    /// `2` = HEVC (default / older host), `1` = H.264, `4` = AV1. Build the decoder from THIS. The
-    /// resolved value honors the client's `preferredCodec` when the host could emit it.
+    /// `2` = HEVC (default / older host), `1` = H.264, `4` = AV1, `8` = PyroWave (only when this
+    /// client opted in). Build the decoder from THIS. The resolved value honors the client's
+    /// `preferredCodec` when the host could emit it.
     public private(set) var resolvedCodec: UInt8 = 2 // PUNKTFUNK_CODEC_HEVC
+
+    /// The session's negotiated wire shard payload (`Welcome.shard_payload`, bytes) — the
+    /// parse-window size for `USER_FLAG_CHUNK_ALIGNED` PyroWave AUs (plan §4.4). Other codecs
+    /// never need it.
+    public private(set) var shardPayload: UInt32 = 1408
     /// The resolved codec as a `VideoCodec` (H.264 / HEVC / AV1) — drives the bitstream framing
     /// (Annex-B NAL parsing vs the AV1 OBU repack).
     public var videoCodec: VideoCodec { VideoCodec(wire: resolvedCodec) }
@@ -452,6 +458,9 @@ public final class PunktfunkConnection {
         var codec: UInt8 = 2 // PUNKTFUNK_CODEC_HEVC
         _ = punktfunk_connection_codec(handle, &codec)
         resolvedCodec = codec
+        var shard: UInt32 = 1408
+        _ = punktfunk_connection_shard_payload(handle, &shard)
+        shardPayload = shard
     }
 
     /// A bandwidth speed-test measurement (see `startSpeedTest`). Partial until `done`.
@@ -790,6 +799,15 @@ public final class PunktfunkConnection {
     public static let codecH264: UInt8 = UInt8(PUNKTFUNK_CODEC_H264)
     public static let codecHEVC: UInt8 = UInt8(PUNKTFUNK_CODEC_HEVC)
     public static let codecAV1: UInt8 = UInt8(PUNKTFUNK_CODEC_AV1)
+    /// PyroWave (opt-in wired-LAN wavelet codec, 8-bit SDR): the host only ever resolves it
+    /// when the client both advertises the bit AND names it `preferredCodec` — never
+    /// auto-selected. Decoded by the Metal wavelet decoder, not VideoToolbox.
+    public static let codecPyroWave: UInt8 = UInt8(PUNKTFUNK_CODEC_PYROWAVE)
+
+    /// `AccessUnit.flags` bit: the AU is shard-aligned self-delimiting chunks (the wire's
+    /// `USER_FLAG_CHUNK_ALIGNED`, PyroWave datagram-aligned mode §4.4) — walk it
+    /// window-by-window at `shardPayload`. (The C `#define` doesn't import into Swift.)
+    public static let userFlagChunkAligned: UInt32 = 64
 
     /// Static HDR mastering metadata (SMPTE ST.2086 + content light level) the host sent for an HDR
     /// session. Mirrors the wire/ABI `PunktfunkHdrMeta`; primaries are in ST.2086 **G, B, R** order,