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

tests/quickshell/settings-window-contract

@@ -29,8 +29,10 @@ hyprctl -j clients | jq -e '.[] | select(.title == "Settings" and .floating == f
 qs ipc call settings page displays >/dev/null
 [[ "$(qs ipc call settings status | jq -r .page)" == "displays" ]] || fail 'Displays page did not route'
 
+# The retired desktop id must keep routing — to bar, the Shell category's
+# first tab, which is where its content went.
 qs ipc call settings page desktop >/dev/null
-[[ "$(qs ipc call settings status | jq -r .page)" == "desktop" ]] || fail 'Desktop page did not route'
+[[ "$(qs ipc call settings status | jq -r .page)" == "bar" ]] || fail 'the retired desktop id did not route to bar'
 
 address="$(hyprctl -j clients | jq -r '.[] | select(.title == "Settings") | .address')"
 hyprctl dispatch "hl.dsp.window.close({ window = \"address:$address\" })" >/dev/null