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

hyprland/hyprland.conf

@@ -123,6 +123,11 @@ bind = $mod, T, exec, $terminal
 bind = $mod, E, exec, $fileManager
 bind = $mod, A, exec, $launcher
 bind = $mod, D, exec, show-desktop-toggle
+
+# Sidebar toggles — mirrors clicking the arrows on BottomBar, via the
+# IpcHandler registered in shell.qml.
+bind = $mod SHIFT, Z, exec, quickshell ipc call sidebars toggleLeft
+bind = $mod SHIFT, X, exec, quickshell ipc call sidebars toggleRight
 bind = $mod, Q, killactive,
 bind = $mod SHIFT, Q, exit,
 bind = $mod, V, togglefloating,
@@ -173,6 +178,24 @@ bind = $mod SHIFT, 8, movetoworkspace, 8
 bind = $mod SHIFT, 9, movetoworkspace, 9
 bind = $mod SHIFT, 0, movetoworkspace, 10
 
+# Function keys — media/volume/brightness. bindl (not bind) so these still
+# work with the screen locked; bindel additionally repeats while held, for
+# the ones you'd actually want to hold down (volume/brightness ramps).
+bindel = , XF86AudioRaiseVolume, exec, wpctl set-volume -l 1.0 @DEFAULT_AUDIO_SINK@ 5%+
+bindel = , XF86AudioLowerVolume, exec, wpctl set-volume @DEFAULT_AUDIO_SINK@ 5%-
+bindl  = , XF86AudioMute, exec, wpctl set-mute @DEFAULT_AUDIO_SINK@ toggle
+bindl  = , XF86AudioMicMute, exec, wpctl set-mute @DEFAULT_AUDIO_SOURCE@ toggle
+# Chained with an OSD call: unlike volume/mic, brightness has no live
+# service Quickshell can react to (DDC/CI writes aren't broadcast
+# anywhere), so the keybind has to tell the OSD explicitly.
+bindel = , XF86MonBrightnessUp, exec, brightness-ctl up && quickshell ipc call osd brightness "$(brightness-ctl get)"
+bindel = , XF86MonBrightnessDown, exec, brightness-ctl down && quickshell ipc call osd brightness "$(brightness-ctl get)"
+bindl  = , XF86AudioPlay, exec, playerctl play-pause
+bindl  = , XF86AudioPause, exec, playerctl play-pause
+bindl  = , XF86AudioStop, exec, playerctl stop
+bindl  = , XF86AudioNext, exec, playerctl next
+bindl  = , XF86AudioPrev, exec, playerctl previous
+
 # Mouse: drag/resize floating windows
 bindm = $mod, mouse:272, movewindow
 bindm = $mod, mouse:273, resizewindow