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/shell.qml

@@ -102,6 +102,7 @@ ShellRoot {
     ClipboardPanel {}
     Cheatsheet {}
     Welcome {}
+    DockPickOverlay { id: dockPicker }
     CaptureOverlay {}
     IntelligenceResult {}
     ActivityPanel {}
@@ -585,6 +586,17 @@ ShellRoot {
         }
     }
 
+    // Adding to the dock from outside the shell -- the launcher's "Add App to
+    // Dock" command opens the picker, and `pin` is the scripted path for
+    // anything that already knows the desktop id.
+    IpcHandler {
+        target: "dock"
+        function pickApp(): void { ShellState.open("dock-picker"); }
+        // false for an id nothing installs: a pin that does not resolve is
+        // simply absent from the dock, so a silent success would be a lie.
+        function pin(id: string): bool { return dockPicker.pin(id); }
+    }
+
     IpcHandler {
         target: "clipboard"
         function toggle(): void { ShellState.toggle("clipboard"); }