feat(quickshell): idle chain, drifting wallpaper, and a few fixes

- Idle is handled in the shell instead of hypridle: the screen dims
  slowly at 4 minutes, locks at 5, powers down at 6, and suspends at 15
  on battery. Idle inhibitors hold every stage off; Super+Shift+I does
  the same by hand and puts a cup on the rail.
- The shell draws the wallpaper (backdrop/), so hyprpaper is gone. The
  picture is drawn a little larger than the screen and drifts with the
  workspace a beat after the windows, and dims a shade while windows are
  open. The path lives in quickshell/wallpaper.
- The lock screen and power menu say "Take your time." instead of the
  NieR slogan.
- hyprpaper is no longer launched twice, the media module keeps the
  player that played last instead of an empty browser tab, and grouped
  windows show thin untitled tabs with their place in the group (2/3)
  in the bar title.
- qt6ct uses Darkly; the package list gains adw-gtk-theme and darkly-bin.

quickshell/services/Media.qml

@@ -10,6 +10,9 @@ Singleton {
     id: root
 
     property string preferredId: ""
+    // The player that was playing most recently, so pausing it keeps it in
+    // the bar instead of handing the slot to whichever player is listed first.
+    property string lastPlayingId: ""
 
     readonly property var players: Mpris.players?.values ?? []
     readonly property bool hasPlayer: active !== null
@@ -22,9 +25,23 @@ Singleton {
             for (const p of players) if (p.dbusName === root.preferredId) return p;
         }
         for (const p of players) if (p.isPlaying) return p;
+        if (root.lastPlayingId !== "") {
+            for (const p of players) if (p.dbusName === root.lastPlayingId) return p;
+        }
+        // Browsers register a player for every tab with a media element, most
+        // of them with no track at all. Prefer one that has something to show.
+        for (const p of players) if (p.trackTitle) return p;
         return players[0];
     }
 
+    // Remember whichever player was playing last. Bound through the active
+    // player, so it updates whenever playback starts anywhere.
+    readonly property string playingId: {
+        for (const p of players) if (p.isPlaying) return p.dbusName;
+        return "";
+    }
+    onPlayingIdChanged: if (root.playingId !== "") root.lastPlayingId = root.playingId
+
     readonly property string title: active?.trackTitle || ""
     readonly property string artist: active?.trackArtist || ""
     readonly property string album: active?.trackAlbum || ""