feat(waybar): right-click volume opens a floating pwvucontrol mixer

Right-clicking the Waybar volume module now opens pwvucontrol (per-app
mixer); left-click still mutes. Adds:

- on-click-right in waybar.nix + all four whole-swap jsoncs (parity)
- hyprland.nix: the config's first windowrule block — float + center the
  mixer (pwvucontrol, with pavucontrol as a fallback class); normal-
  priority list so a downstream windowrule concatenates
- pwvucontrol in the template home.packages

pwvucontrol is PipeWire-native + GTK4/libadwaita, so it themes via the
portal color-scheme like Amberol. app-id verified from the built package.
This settles the windowrule pattern/placement; item 41 is now just
broadening the float set. Right-click→float→center is a V3 session check.

Co-Authored-By: Claude Opus 4.8 <noreply@anthropic.com>

modules/home/waybar.nix

@@ -172,6 +172,10 @@ let
       format-muted = "󰝟";
       format-icons.default = [ "󰕿" "󰖀" "󰕾" ];
       on-click = "wpctl set-mute @DEFAULT_AUDIO_SINK@ toggle";
+      # Right-click → the full mixer (per-app volumes) in a floating window
+      # (item 35). pwvucontrol ships in the template suite; the Hyprland
+      # windowrule floats it. Keep in sync with the whole-swap jsoncs.
+      on-click-right = "pwvucontrol";
     };
 
     # Idle inhibitor (caffeine): click 󰾪 → 󰅶 to hold the screen awake —