Add WAV playback example

[iancharest]

Summary

• Add examples/play_wav.py for dependency-free WAV playback.
• Include a mono 48 kHz 32-bit float WAV example clip.
• Support PCM WAV and IEEE float WAV loading without relying on Python's wave module for float WAV.
• Remove runtime resampling to avoid interpolation artifacts and clipping.
• Stream playback with prebuffering and queue-aware pacing to avoid underruns/crackle.
• Keep WAV assets out of source distributions; the sample clip is repository-only.

Validation

• PYTHONPATH=src python3 -m unittest discover -s tests
• python3 -m compileall -q src tests examples
• PYTHONPATH=src python3 examples/play_wav.py --duration 5 --volume 0.25
• 5-second playback smoke test reported underruns=0 and overruns=0.