audio.cpp 0.6 adds MiniMax-H3 text2audio, dots.tts, and more audio models

audio.cpp 0.6 adds five model families: dots.tts, NeuTTS-2e, MuScriptor (Music to MIDI), MiniMax-H3, and SenseVoice-Small, bringing the total to 49. MiniMax-H3 text2audio runs up to 3x realtime, MiniMax-Music3 is included as a preview, and 5+ demos ship with the release.