Adds negotiated 5.1/7.1 surround to the punktfunk/1 protocol and every client
(previously stereo-only):
- core: new shared `audio` layout table (LAYOUT_51/71 + identity multistream
mapping, canonical wire order FL FR FC LFE RL RR SL SR); Hello/Welcome
`audio_channels` negotiation via the trailing-byte back-compat pattern (old
peers fall back to stereo); C-ABI `punktfunk_connect_ex6`,
`punktfunk_connection_audio_channels`, and in-core multistream decode
`punktfunk_connection_next_audio_pcm` for embedders without a multistream
Opus decoder. Real-libopus channel-identity round-trip test.
- host: native audio thread captures + Opus-(multi)stream-encodes at the
negotiated count (with a cross-session cached-capturer channel-mismatch fix);
GameStream surround unified onto the safe `opus::MSEncoder`, dropping
`audiopus_sys` (~4 unsafe blocks) and un-gating Windows GameStream surround;
WASAPI loopback capture relaxed to 2/6/8 with the correct dwChannelMask.
- clients: Linux (PipeWire), Windows (WASAPI), Android (AAudio) decode via
`opus::MSDecoder` + render multichannel; Apple decodes in-core to PCM →
AVAudioEngine with an explicit wire-order channel layout; each gains a
Stereo/5.1/7.1 setting. `punktfunk-probe --audio-channels N` is the headless
validator.
Verified on Linux: core/host/linux/probe test suites + the Android Rust
(cargo-ndk) build, clippy -D warnings, and rustfmt all green. Windows/Apple
builds, all on-glass checks, and the live native loopback are pending (CI / a
free box).
Also lands the concurrent in-tree HEVC 4:4:4 host work (PUNKTFUNK_444): it
shares the same touched files (quic.rs, punktfunk1.rs, encode/*, ...) and so
cannot be committed separately from the surround changes.
Co-Authored-By: Claude Opus 4.8 <noreply@anthropic.com>
