# Audio comparison for duplicate review

## Problem

Filenames alone are weak evidence. DJs need to hear each candidate and locate it
on disk before deciding which copy is authoritative.

## Design

Exact-duplicate and cloud-conflict groups expose a shared audio player with a
preview action for each file. Switching files reuses the same player, making
back-to-back comparison quick. A separate action reveals the selected file in
macOS Finder.

The browser never receives unrestricted filesystem access. Each analyzed audio
path gets a short, process-local HMAC token. Preview and Finder endpoints reject
altered, expired, missing, non-audio, or otherwise unsigned paths. Audio serving
supports HTTP byte ranges so playback can seek without loading an entire track.

## Edge cases

- A file moved after analysis is rejected.
- Forged or stale tokens cannot select another local file.
- Preview controls remain useful if autoplay is blocked because native audio
  controls stay visible.
- Finder failures are reported beside the button without affecting analysis.

## Tests

- Valid signed audio resolves to the analyzed file.
- A modified token is rejected.
- Duplicate detail payloads include preview and Finder controls for every file.