feat(mime): open audio files in Amberol, not mpv

mpv (video) and amberol (audio) are both already in the template suite;
the gap was mime wiring — audio/* still resolved to mpv.desktop. Repoint
the audio types to io.bassi.Amberol.desktop (id verified against the
built package) and broaden coverage to mp3/flac/ogg/opus/wav/m4a/aac,
both canonical and x- names. Video stays on mpv. Degrades to mpv if a
downstream drops Amberol from the suite.

Co-Authored-By: Claude Opus 4.8 <noreply@anthropic.com>

agent/HARDWARE-QUEUE.md

@@ -236,6 +236,10 @@ QA machine), the **T14s** (webcam case).
       unchanged (the bar still reserves its space). Accepted trade-off
       of `layer: bottom`: a floating window dragged over the top strip
       can now overlap the bar — confirm that's the only regression.
+- [ ] **Audio opens in Amberol** (iteration #60, item 37) — after
+      `home-update`: double-click an mp3/flac/ogg (or `xdg-open song.mp3`)
+      → it opens in Amberol, not mpv; video files still open in mpv.
+      (`xdg-mime query default audio/mpeg` → io.bassi.Amberol.desktop.)
 - [ ] **Capture-to-file keybinds** (iteration #59, item 38) — after
       `home-update` + relogin: SHIFT+Print prompts a region select then
       saves a PNG under ~/Pictures/Screenshots (toast shows the path);