Handle bidirectional AEC reference lag

[ComputelessComputer]

Delay either the speaker reference or mic input based on sync lag, reset AEC state on alignment changes, and cover negative-lag detection in audio sync tests.

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Note

Medium Risk
Changes live capture AEC alignment and Soniqo mic gating, which can affect echo cancellation quality and transcript content if thresholds are wrong; scope is audio pipeline only, not auth or data storage.

Overview
AEC capture now aligns mic and speaker using sync lag in both directions: positive lag delays the speaker reference, negative lag delays the mic, and AEC state resets when that alignment changes. Processing uses the aligned pair instead of only shifting the speaker.

audio-sync gains regression tests that negative lag is estimated (GCC-PHAT) and that the sync probe can lock on it.

Soniqo live transcription is refactored onto the same MixedMessage single/dual channels as other adapters (dropping SoniqoAudioMsg). In mic+speaker mode, an echo gate zeros mic chunks that look like delayed, highly correlated speaker bleed before they are sent for transcription, with unit tests for suppress vs keep cases.

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Cursor Bugbot has reviewed your changes using default effort and found 1 potential issue.

There are 2 total unresolved issues (including 1 from previous review).

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