refactor(mpris): enrich metadata across equivalent players (#2928)

* fix(mpris): enrich metadata across equivalent players

* fix(mpris): address review feedback on source stealing and title stripping

- _bestPlayingPlayer: when the active player is playing but not
  controllable, only hand ownership to a controllable peer that passes
  isSameTrack; unrelated players can no longer steal the active source.
- displayTrackTitle: keep the full trackTitle for display. Suffix
  stripping now only applies to the isSameTrack matching key, and only
  for a known app-name allowlist (YouTube, SoundCloud, browsers, etc.)
  so legitimate titles containing ' | ' are never mangled.

Co-Authored-By: Claude Fable 5 <noreply@anthropic.com>

---------

Port 1.5

quickshell/Modules/DankDash/MediaPlayerTab.qml

@@ -493,7 +493,7 @@ Item {
                     }
 
                     StyledText {
-                        text: activePlayer?.trackAlbum || ""
+                        text: MprisController.stableAlbum
                         font.pixelSize: Theme.fontSizeSmall
                         color: Theme.surfaceTextSecondary
                         width: parent.width