audio_stream.py: Added focus_side property. When set, the stream
yields from the focused side regardless of energy (attention lock).
When None, falls back to energy-based auto selection.
multi_speaker.py: When beams lock onto 2 speakers, sets audio focus
to the target speaker's side. Auto-switches target when the current
target goes silent and the other starts talking. Manual focus via API.
headmic.py: New endpoint POST /speakers/focus?speaker=0|1 to manually
switch attention. /speakers/tracked now shows is_target, target_speaker,
and audio_focus fields.
The cocktail party effect: when 2 people are talking, the audio feed
to Porcupine/VAD/transcription comes from the target speaker's direction,
suppressing the other. XVF3800 beam gating silences the non-speaking beam,
and audio_stream focus locks the ear facing the target.
Co-Authored-By: Claude Opus 4.6 (1M context) <noreply@anthropic.com>
