OMI Audio extension for glTF

Another OMI-based extension, this time for positional audio mixing. Again, Claude-coded, using the OMI/KHR audio extensions for glTF as the base model and then implementing the actual mixing using Numpy. Supports mp3, wav, opus and flac inputs and stereo (headset) outputs. Up on github as omi_audio and on PyPI as omi_audio as well. This is loosely the same model as Web Audio's Panner Node. The…