# BUILD_SPEC — synthetic-bad-spec (TEST FIXTURE — DO NOT DISPATCH)

## Phase 1: Add new sidecar writer for audio shots

### Files to create
- `recoil/pipeline/_lib/audio_sidecar.py`

### Description
Create a new sidecar writer function `write_audio_sidecar()` specifically for audio shot
sidecars. Audio shots have different fields from video shots, so a new dedicated writer
is cleaner than extending populate_sidecar.

### Implementation
Create `write_audio_sidecar(shot_id, audio_path, duration_s, model)` that writes a
minimal sidecar with only audio-relevant fields.