Add terminal EQ meter to WAV example

[iancharest]

Summary

• Add optional --eq five-band terminal meter to examples/play_wav.py.
• Render an in-place dynamic horizontal five-row EQ display in real terminals.
• Fall back to compact single-line updates when stdout is not a TTY.
• Keep the meter dependency-free and computed from chunks already being streamed.
• Add --eq-width and --eq-refresh controls.
• Document the flag in the README.

Validation

• PYTHONPATH=src python3 -m unittest discover -s tests
• python3 -m compileall -q src tests examples
• PYTHONPATH=src python3 examples/play_wav.py --duration 3 --volume 0.25 --eq --eq-width 18
• Playback smoke test reported underruns=0 and overruns=0.