Module echo 

Echo cancellation for voice pipeline.

Prevents the system from hearing its own TTS output during Talk Mode. Uses a reference signal (the TTS audio) to cancel echoes from the mic input.

Current implementation: stub (passthrough). Real AEC will use webrtc-audio-processing or a custom delay-line canceller in a future phase.

Structs

EchoCanceller

Echo canceller state.

EchoCancellerConfig

Configuration for echo cancellation.