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/services/media/BarWidget.qml

@@ -40,7 +40,7 @@ BarWidget {
       font.pixelSize: Style.font.body
       Behavior on color {
         enabled: !root.bar || root.bar.foregroundAnimationEnabled
-        ColorAnimation { duration: 160 }
+        ColorAnimation { duration: Style.duration(160) }
       }
     }
 
@@ -65,7 +65,9 @@ BarWidget {
 
         NumberAnimation on x {
           id: scrollAnim
-          running: labelText.needsScroll && !root.popupOpen && !root.bar.vertical
+          running: labelText.needsScroll && !root.popupOpen && !root.bar.vertical && !Style.reduceMotion
+          // Stopped for reduced motion, the title reads from its start again.
+          onRunningChanged: if (!running && Style.reduceMotion) labelText.x = 0
           loops: Animation.Infinite
           duration: Math.max(6000, labelText.implicitWidth * 25)
           from: scrollClip.width