Fix: dialog scroll, isDirty false positive, mobile edit btn, widget copy

Five fixes:

1. Dialog mobile scroll: DialogContent now has max-h-[calc(100dvh-2rem)]
   overflow-y-auto so dialogs that don't fit on screen can scroll
   instead of clipping their footer (and Cancel button) off-screen.

2. isDirty false positive: WidgetConfigDialog's SheetForm used
   isDirty={draft !== null} which was true the moment you opened edit
   mode, even with no changes. Now stores a draftBaseline at startEdit
   time and compares JSON.stringify(draft) !== JSON.stringify(baseline).
   The discard-confirmation only appears when something actually changed.

3. Mobile edit button always visible: the widget card's edit button was
   opacity-0 group-hover:opacity-100 (hover-only). Changed to
   md:opacity-0 md:group-hover:opacity-100 — always visible below md,
   hover-reveal at md+.

4. Copy button for referenced widgets: WidgetInstanceCard gains an onCopy
   prop. On the Dashboard, referenced widgets get a Copy icon button that
   triggers detachRef (creates an independent clone). The edit button on
   referenced widgets edits the original (shared config).

5. ConfirmDialog Cancel: fixed by #1 (the Cancel button was off-screen
   on mobile dialogs that couldn't scroll).

128 tests pass; lint/build green.

frontend/src/components/WidgetConfigDialog.tsx

@@ -227,6 +227,7 @@ export function WidgetConfigDialog({
 	const [existingSearch, setExistingSearch] = useState("");
 
 	const [draft, setDraft] = useState<Draft | null>(null);
+	const [draftBaseline, setDraftBaseline] = useState<Draft | null>(null);
 
 	// When editWidgetId is set and the dialog opens, auto-enter edit mode for
 	// that widget (instead of showing the list view).
@@ -266,7 +267,7 @@ export function WidgetConfigDialog({
 	}
 
 	function startEdit(instance: WidgetInstance) {
-		setDraft({
+		const d: Draft = {
 			id: instance.id,
 			serviceId: instance.service_id,
 			widgetKind: instance.widget_kind,
@@ -274,11 +275,14 @@ export function WidgetConfigDialog({
 			config: instance.config,
 			enabled: instance.enabled,
 			sortOrder: instance.sort_order,
-		});
+		};
+		setDraft(d);
+		setDraftBaseline(d);
 	}
 
 	function reset() {
 		setDraft(null);
+		setDraftBaseline(null);
 	}
 
 	async function saveDraft() {
@@ -701,7 +705,11 @@ export function WidgetConfigDialog({
 				onCancel={draft ? reset : () => handleClose(false)}
 				saveLabel={draft ? "Save widget" : "Done"}
 				isPending={draft ? saveWidget.isPending : false}
-				isDirty={draft !== null}
+				isDirty={
+					draft !== null && draftBaseline !== null
+						? JSON.stringify(draft) !== JSON.stringify(draftBaseline)
+						: draft !== null && draft?.id === undefined
+				}
 			>
 				<div className="flex flex-col gap-4">{draftBody}</div>
 			</SheetForm>

frontend/src/components/WidgetInstance.tsx

@@ -1,6 +1,6 @@
 import { Alert, AlertDescription } from "@/components/ui/alert";
 import { Button } from "@/components/ui/button";
-import { Settings2 } from "lucide-react";
+import { Settings2, Copy } from "lucide-react";
 import { useServiceInstances } from "../hooks/useServices";
 import { resolveWidget } from "../integrations/registry";
 import type { WidgetInstance } from "../types";
@@ -8,31 +8,51 @@ import { SectionCard } from "./SectionCard";
 
 interface Props {
 	widget: WidgetInstance;
-	/** When provided, a hover-reveal edit button appears in the top-right corner. */
+	/** When provided, an edit button appears in the top-right corner (hover on desktop, always on mobile). */
 	onEdit?: (widgetId: string) => void;
+	/** When provided, a copy/detach button appears next to edit (for referenced widgets). */
+	onCopy?: (widgetId: string) => void;
 }
 
-export function WidgetInstanceCard({ widget, onEdit }: Props) {
+export function WidgetInstanceCard({ widget, onEdit, onCopy }: Props) {
 	const { data: services = [] } = useServiceInstances();
 	const resolved = resolveWidget(widget, services);
 
+	// Edit + copy buttons: always visible on mobile (below md), hover-reveal on desktop.
+	const actionButtons = (
+		<div className="absolute right-2 top-2 z-10 flex items-center gap-1">
+			{onCopy ? (
+				<Button
+					variant="ghost"
+					size="icon-sm"
+					className="opacity-100 transition-opacity md:opacity-0 md:group-hover:opacity-100 mobile-touch-target"
+					onClick={() => onCopy(widget.id)}
+					aria-label="Create independent copy"
+				>
+					<Copy className="h-4 w-4" />
+				</Button>
+			) : null}
+			{onEdit ? (
+				<Button
+					variant="ghost"
+					size="icon-sm"
+					className="opacity-100 transition-opacity md:opacity-0 md:group-hover:opacity-100 mobile-touch-target"
+					onClick={() => onEdit(widget.id)}
+					aria-label="Edit widget"
+				>
+					<Settings2 className="h-4 w-4" />
+				</Button>
+			) : null}
+		</div>
+	);
+
 	if (!resolved) {
 		const label = widget.service_id
 			? `Unknown widget: ${widget.widget_kind} (service-bound)`
 			: `Unknown widget: ${widget.widget_kind} (built-in)`;
 		return (
 			<div className="group relative">
-				{onEdit ? (
-					<Button
-						variant="ghost"
-						size="icon-sm"
-						className="absolute right-2 top-2 z-10 opacity-0 transition-opacity group-hover:opacity-100 mobile-touch-target"
-						onClick={() => onEdit(widget.id)}
-						aria-label="Edit widget"
-					>
-						<Settings2 className="h-4 w-4" />
-					</Button>
-				) : null}
+				{(onEdit || onCopy) ? actionButtons : null}
 				<SectionCard title={widget.title}>
 					<Alert>
 						<AlertDescription>{label}</AlertDescription>
@@ -45,17 +65,7 @@ export function WidgetInstanceCard({ widget, onEdit }: Props) {
 	const Component = resolved.component;
 	return (
 		<div className="group relative">
-			{onEdit ? (
-				<Button
-					variant="ghost"
-					size="icon-sm"
-					className="absolute right-2 top-2 z-10 opacity-0 transition-opacity group-hover:opacity-100 mobile-touch-target"
-					onClick={() => onEdit(widget.id)}
-					aria-label="Edit widget"
-				>
-					<Settings2 className="h-4 w-4" />
-				</Button>
-			) : null}
+			{(onEdit || onCopy) ? actionButtons : null}
 			<Component
 				widget={widget}
 				refreshIntervalMs={resolved.refreshIntervalMs}

frontend/src/components/ui/dialog.tsx

@@ -59,7 +59,7 @@ function DialogContent({
       <DialogPrimitive.Content
         data-slot="dialog-content"
         className={cn(
-          "fixed top-1/2 left-1/2 z-50 grid w-full max-w-[calc(100%-2rem)] -translate-x-1/2 -translate-y-1/2 gap-4 rounded-xl bg-popover p-4 text-sm text-popover-foreground ring-1 ring-foreground/10 duration-100 outline-none sm:max-w-sm data-open:animate-in data-open:fade-in-0 data-open:zoom-in-95 data-closed:animate-out data-closed:fade-out-0 data-closed:zoom-out-95",
+          "fixed top-1/2 left-1/2 z-50 grid w-full max-w-[calc(100%-2rem)] max-h-[calc(100dvh-2rem)] overflow-y-auto -translate-x-1/2 -translate-y-1/2 gap-4 rounded-xl bg-popover p-4 text-sm text-popover-foreground ring-1 ring-foreground/10 duration-100 outline-none sm:max-w-sm data-open:animate-in data-open:fade-in-0 data-open:zoom-in-95 data-closed:animate-out data-closed:fade-out-0 data-closed:zoom-out-95",
           className
         )}
         {...props}