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/JOURNAL.md

@@ -17,6 +17,22 @@ Template:
 
 ---
 
+## 2026-07-07 — Audio mime → Amberol (iteration #60, item 37)
+- **Task:** BACKLOG item 37 — default video + audio players + mime. On
+  inspection both players were already installed: mpv (video) and amberol
+  (a prior template add). So the real gap was the *mime wiring* — audio
+  files still opened in mpv (mime.nix mapped audio/* → mpv.desktop).
+- **Fix:** `modules/home/mime.nix` — repoint the audio/* types to
+  `io.bassi.Amberol.desktop` (verified against the built package's
+  actual .desktop id + its MimeType set) and broaden coverage (mp3/flac/
+  ogg/opus/wav/m4a/aac, both canonical and x- names). Video stays mpv.
+- **Why Amberol:** GTK4/libadwaita, so it themes via the portal
+  color-scheme the distro already wires; minimal, purpose-built for
+  "open a file → play." Degrades to mpv if a downstream drops it.
+- **Verified:** V0 green; entries mirror the existing working image/video
+  mappings, desktop id confirmed from the realised package. Runtime GIO
+  resolution (double-click an mp3 → Amberol) is a V3 session check (queued).
+
 ## 2026-07-07 — Capture-to-file keybinds (iteration #59, item 38)
 - **Task:** BACKLOG item 38 — direct keybinds for region→file and
   screen→file (the Capture *menu* already had both "→ file" rows).