Per plan §2.1: a self-contained stateful subsystem does not belong in the
audio trait facade. Move MicPump + its PumpTuning/PUMP_TUNING, the
drain_sleep/pump_thread loop, MIC_CHANNELS/MIC_QUEUE_CAP, and the six pump
unit tests out of audio.rs into audio/mic_pump.rs. audio.rs keeps the
AudioCapturer/VirtualMic traits, their open_* factories, and the sample
constants. Re-export via `pub use mic_pump::MicPump` so crate::audio::MicPump
stays byte-stable (only consumer: punktfunk1.rs). Pure code-move; verified
clippy 0/0 + 6/6 pump tests green on Linux (home-worker-5).
Co-Authored-By: Claude Opus 4.8 (1M context) <noreply@anthropic.com>
enricobuehler
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