theme: soften the YoRHa shapes; SUPER+D opens the dashboard

The square markers, block meters and hard-cornered fills read as boxy
next to the porthole. The desktop is now soft throughout: the porthole
is the shape everything is built around and every smaller surface echoes
it.

- Theme gains radiusS / radiusM / radiusL. radiusL is frameRadius - padS,
  so anything inset padS inside one of the frame's curves is concentric
  with it.
- P5Panel and Skew draw rounded rectangles (Geom.roundedRect) whenever
  they neither lean nor are chopped, which is always now; the polygon
  path is kept for shapes brought back on purpose.
- Markers are dots; workspace pips, toggles, transport and media chips,
  notification actions and today's date are pills or discs; the slider
  handle is round. Meters are one continuous rounded line that glides to
  its level instead of a row of segments.
- Album art is rounded with ClippingRectangle in the bar, the media
  popout and the dashboard.
- Free-standing panels (launcher, ask) drop the corner brackets and take
  the frame radius.
- Fix: a hovered notification's wash was a full-bleed square, so in the
  drawer's bottom corner it ran past the drawer's curve. It is inset by
  padS/2 and rounded by radiusL, which keeps it inside the curve.

Hyprland: the discord special workspace and its window rule are gone,
SUPER+S stays the only scratchpad, and SUPER+D now opens the dashboard
(it was on SUPER+I).

Co-Authored-By: Claude Opus 5.5 <noreply@anthropic.com>

quickshell/components/P5Slider.qml

@@ -2,8 +2,7 @@ import QtQuick
 import "root:/config"
 import "root:/components"
 
-// Hairline slider with a square handle, the NieR settings-menu slider. Drag or
-// click anywhere on the rail.
+// Hairline slider with a round handle. Drag or click anywhere on the rail.
 Item {
     id: root
 
@@ -68,6 +67,7 @@ Item {
     Skew {
         id: handle
         width: height
+        radius: height / 2
         height: root.activeFocus || hover.hovered || drag.active ? 12 : 10
         color: root.enabled ? Theme.text : Theme.treatmentDisabledText
         anchors.verticalCenter: parent.verticalCenter