meeting-assistant/openspec/changes/archive/2026-05-29-add-audio-headroom-and-azure-aec/tasks.md

1. Implementation

• Keep Microsoft MAS package/assets available without an Azure AEC runtime feature flag.
• Capture and buffer microphone/system input streams separately before mixing.
• Clean microphone chunks with a local echo cancellation stage before mixing.
• Mix cleaned microphone and system audio by addition with configurable gains.
• Keep temporary recording output to the mixed WAV; do not persist diagnostic channel sidecars.
• Add focused tests for local echo cleanup, additive mixing, aligned mixing, and mixed-only temporary recording.

2. Verification

• Run focused tests.
• Run dotnet test MeetingAssistant.slnx.
• Run openspec validate add-audio-headroom-and-azure-aec --strict.