Show OSD and sync touchpad steps when scrolling bar widgets (audio, monitor) (#6421)

* Show OSD and sync touchpad steps when scrolling bar widgets

Scrolling the volume or brightness icon in the bar changed the value
directly without ever calling omarchy-osd, so only the keyboard media
keys showed the popup. On top of that, a touchpad's stream of many
small wheel events per finger-drag wasn't matched to a mouse's single
±120 notch per click, so touchpad scrolling felt uncoordinated and
uneven next to the keyboard/mouse behavior.

- shell/plugins/panels/audio/Panel.qml: accumulate raw wheel delta and
  only apply a step once it crosses a full mouse-notch's worth, so
  touchpad and mouse move the volume in identical 5% increments, and
  ping the OSD each time a step actually lands.
- shell/plugins/panels/monitor/Panel.qml: same accumulator for
  brightness, with a 5% floor so scrolling down can never blank the
  screen.
- shell/plugins/osd/Osd.qml: animate the progress bar's width instead
  of snapping, so successive steps glide smoothly.

* Potential fix for pull request finding

Co-authored-by: Copilot Autofix powered by AI <175728472+Copilot@users.noreply.github.com>

* Fix bar wheel OSD behavior

* Normalize scaled wheel events

---------

Co-authored-by: Copilot Autofix powered by AI <175728472+Copilot@users.noreply.github.com>
Co-authored-by: David Heinemeier Hansson <david@hey.com>

shell/Commons/Util.qml

@@ -17,6 +17,17 @@ QtObject {
     return clamp(value, 0, 1)
   }
 
+  function wheelSteps(accumulator, delta) {
+    // Some mouse/compositor combinations scale a single notch well beyond
+    // Qt's conventional 120 units. Keep one event to one step while still
+    // accumulating the smaller deltas emitted by touchpads.
+    delta = Math.max(-120, Math.min(120, delta))
+    if (accumulator * delta < 0) accumulator = 0
+    var total = accumulator + delta
+    var steps = total < 0 ? Math.ceil(total / 120) : Math.floor(total / 120)
+    return { steps: steps, remainder: total - steps * 120 }
+  }
+
   // Compose a base color with an opacity. Accepts a color object or a hex
   // string; null/undefined yields transparent black at the requested alpha.
   function alpha(c, opacity) {