Add on-screen display, sidebar keybinds, function keys, gh package

- Add Osd.qml: themed top-center popup for volume/mic/brightness/media
  changes. Volume and mic react directly to Pipewire so they fire for
  any change, not just our own keybinds; brightness is notified
  explicitly (no live service exists for DDC/CI writes); media is
  driven by two playerctl --follow watchers (status + metadata) so
  track changes, pause/resume, and stop all show correctly without
  double-firing
- Add Super+Shift+Z/X to toggle the Left/RightBar sidebars, via a new
  Quickshell IpcHandler wired to the same expand/collapse logic as the
  BottomBar arrows
- Add function-key binds for volume up/down/mute, mic mute, brightness
  up/down, and media play/pause/stop/next/prev (wpctl/playerctl);
  extend brightness-ctl with relative up/down steps for both the
  backlight and DDC/CI paths
- Add gh and playerctl to packages

dotfiles/quickshell/shell.qml

@@ -9,9 +9,11 @@
 // menu silently does nothing.
 import QtQuick
 import Quickshell
+import Quickshell.Io
 
 ShellRoot {
     PolkitDialog {}
+    Osd {}
 
     Variants {
         model: Quickshell.screens
@@ -22,6 +24,22 @@ ShellRoot {
             LeftBar { id: leftBarInstance; screen: modelData }
             RightBar { id: rightBarInstance; screen: modelData }
             BottomBar { screen: modelData; leftBar: leftBarInstance; rightBar: rightBarInstance }
+
+            // Lets Hyprland keybinds (Super+Shift+Z/X, see hyprland.conf)
+            // toggle the sidebars via `quickshell ipc call sidebars
+            // toggleLeft/toggleRight` — same open/close behavior as
+            // clicking the arrows on BottomBar.
+            IpcHandler {
+                target: "sidebars"
+                function toggleLeft(): void {
+                    leftBarInstance.expanded = !leftBarInstance.expanded;
+                    if (!leftBarInstance.expanded) leftBarInstance.activePanel = "";
+                }
+                function toggleRight(): void {
+                    rightBarInstance.expanded = !rightBarInstance.expanded;
+                    if (!rightBarInstance.expanded) rightBarInstance.activePanel = "";
+                }
+            }
         }
     }
 }