Make Shell a category, the bar legible, and the dock a real dock

Desktop & Dock becomes Shell — Bar, Dock, Control Center, Tiling,
Workspaces — the home for everything Quickshell draws. The settings-
management cluster moves to System as Sync & Backup, Appearance's
Shell tab dissolves, and 24-hour time finally lives on Date & Time,
which always owned it.

The bar gets what it never had: a way to survive the wallpaper. A
second neutral text family (follow theme, or forced light or dark),
a one-layer shadow under every glyph, and a gradient scrim for
wallpapers nothing else survives — all off by default, pixel-identical
until asked. Widgets earn toggles (weather, media, clipboard, calendar
countdown), the vitals cluster stops leaving a dead pill behind, and
Control Center's sections learn to step aside.

The dock graduates from MVP: a context menu with window rows, pin,
unpin, quit and new-window; scroll an icon to cycle its windows; drag
to reorder on the dock itself; hover previews with one-shot captures;
and "Add App to Dock" in the launcher. Three real bugs died en route —
menus that slid away with the autohide, a readonly-property crash on
every menu open, and a drag that drifted half a slot per icon on side
docks. The pinned-apps editor in Settings becomes a drag strip.

166 contracts; the full suite is green except two live display and
switcher tests that cannot run behind a locked session — re-verified
on unlock.

Claude-Session: https://claude.ai/code/session_01Ms2FbjQy31TVf3CEvQhGM8

config/dot/quickshell/modules/bar/AgentUsageWidget.qml

@@ -27,8 +27,8 @@ Pill {
 
     visible: Settings.showAgentUsage && AgentUsage.available
 
-    onActivated: ShellState.openSettings("appearance")
-    onSecondaryActivated: ShellState.openSettings("appearance")
+    onActivated: ShellState.openSettings("bar")
+    onSecondaryActivated: ShellState.openSettings("bar")
 
     Row {
         spacing: 4
@@ -39,7 +39,7 @@ Pill {
             color: {
                 if (AgentUsage.headline >= 90) return Theme.danger;
                 if (AgentUsage.headline >= 75) return Theme.warn;
-                return Theme.fgDim;
+                return Theme.barFgDim;
             }
             font.family: Theme.fontMono
             font.pixelSize: Theme.fontSize
@@ -48,7 +48,7 @@ Pill {
         Text {
             anchors.verticalCenter: parent.verticalCenter
             text: AgentUsage.headline + "%"
-            color: Theme.fg
+            color: Theme.barFg
             font.family: Theme.fontFamily
             font.pixelSize: Theme.fontSizeSmall
             font.features: Theme.tabularFigures