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/services/ShellState.qml

@@ -17,7 +17,7 @@ Singleton {
     id: root
 
     // Exactly one of these may be non-empty at a time.
-    // "" | "overview" | "quicksettings" | "notifications" | "clipboard" | "capture" | "activity" | "powermenu" | "cheatsheet" | "welcome"
+    // "" | "overview" | "quicksettings" | "notifications" | "clipboard" | "capture" | "activity" | "powermenu" | "cheatsheet" | "welcome" | "dock-picker"
     property string activeOverlay: ""
 
     readonly property bool overviewOpen: activeOverlay === "overview"
@@ -29,6 +29,7 @@ Singleton {
     readonly property bool powerMenuOpen: activeOverlay === "powermenu"
     readonly property bool cheatsheetOpen: activeOverlay === "cheatsheet"
     readonly property bool welcomeOpen: activeOverlay === "welcome"
+    readonly property bool dockPickerOpen: activeOverlay === "dock-picker"
 
     // Settings is a normal application window rather than a transient overlay.
     // It can stay open while Quick Settings or the notification center appears.