Reorganizes src/dusk/audio/: individual stream implementations
(audiostream, audiostreampcm, audiostreammp3, audiostreammp3decodersw)
move into audio/stream/, and a new audio/mixer/ holds a channel-based
playback queue (audiomixer.c/.h) for future use - not yet wired into
the engine.
Fixes needed to keep the tree buildable after the move:
- A stray duplicate of audiostreammp3decodersw.c/.h was left at the old
flat path; removed in favor of the canonical copy in stream/.
- Updated every #include "audio/audiostream*.h" and the two platform
CMakeLists.txt (dusklinux, duskdolphin) that still pointed at the old
flat location.
- audiomixer.c/.h didn't compile: audiomixerqueue_t was referenced but
never defined (audiomixerchanneldata_t has the matching fields), a
trailing comma in audioMixerPlayLooped's parameter list is illegal in
C, and `file` was declared as an array of pointers instead of a char
buffer.
Co-Authored-By: Claude Sonnet 5 <[email protected]>