Add a no-animations mode, on by default in VMs (#13550)

A machine without a GPU, like most VMs, renders through llvmpipe on the
CPU, where every animated frame and every translucent window costs. In a
VM, opening and closing a terminal took ~5s of CPU; a panel ~3.4s.

omarchy toggle animations (also under Toggle > Animations) places a Hyprland
flag that turns off animations, blur and shadows and makes windows opaque.
The shell follows Hyprland's animations:enabled, rereading it on every
config reload: its one-shot animations run for Style.duration(ms), which
is then 0, and its spinners, pulses and title marquee hold still. A new
install in a VM starts with the flag in place.

Measured in the ISO test VM (llvmpipe), CPU per interaction:
terminal open+close 5000ms -> 481ms, workspace switch 1670ms -> 409ms,
audio panel 3446ms -> 796ms, volume OSD 2324ms -> 584ms, menu 2028ms ->
1241ms.

Co-authored-by: Claude Opus 5.5 <noreply@anthropic.com>

shell/plugins/agents/Panel.qml

@@ -788,7 +788,7 @@ Panel {
       color: meter.alarming ? root.urgent : root.foreground
 
       Behavior on width {
-        NumberAnimation { duration: 160; easing.type: Easing.OutCubic }
+        NumberAnimation { duration: Style.duration(160); easing.type: Easing.OutCubic }
       }
     }
 
@@ -837,7 +837,7 @@ Panel {
         color: dayRow.today ? root.foreground : root.alpha(root.foreground, 0.55)
 
         Behavior on width {
-          NumberAnimation { duration: 160; easing.type: Easing.OutCubic }
+          NumberAnimation { duration: Style.duration(160); easing.type: Easing.OutCubic }
         }
       }
     }
@@ -894,7 +894,7 @@ Panel {
       color: root.alpha(root.foreground, 0.14)
 
       Behavior on width {
-        NumberAnimation { duration: 160; easing.type: Easing.OutCubic }
+        NumberAnimation { duration: Style.duration(160); easing.type: Easing.OutCubic }
       }
     }