Mobile message compose + WidgetConfigDialog SheetForms (Slice 8)

Below md, both the message-compose Dialog and the WidgetConfigDialog
render inside a SheetForm instead of a centered Dialog.

Message compose (UsersPage.impl.tsx): the form body (subject, formatting
toolbar, HTML textarea, preview, attachments) is extracted into a shared
composeBody const consumed by both SheetForm (mobile) and Dialog
(desktop). SheetForm wired with title, onSave=handleSend (which already
closes on success per R4.5), onCancel=closeCompose, isPending,
saveDisabled, saveLabel='Send message'.

WidgetConfigDialog: the draftBody const is shared between branches. The
two-mode flow (list vs draft) maps to dynamic SheetForm props -- list
mode ('Dashboard widgets' / Done / Cancel both close), draft mode
('Add/Edit widget' / Save widget / Cancel=reset back to list). The
inline Back/Save buttons are hidden on mobile (!isMobile) since the
SheetForm footer provides them.

Desktop (md+) is token-identical for both components -- the
isComposeMobile (900px) fullscreen styling on compose is preserved for
the 768-900px band. The large diff (~860 lines) is dominated by
extraction/re-indentation of shared form bodies into consts; the
behavioral delta is ~80 lines.

Tests: 3 new (compose mobile send/subject, WidgetConfigDialog desktop +
mobile titles/Done). 116 tests pass; lint/build green.

Refs openspec/changes/mobile-responsive-parity/ (spec R4, tasks slice 8).

frontend/src/components/WidgetConfigDialog.tsx

@@ -26,6 +26,8 @@ import {
 } from "../hooks/useWidgets";
 import { useServiceInstances } from "../hooks/useServices";
 import { useTasks } from "../hooks/useSettings";
+import { useIsMobile } from "../hooks/useIsMobile";
+import { SheetForm } from "@/components/ui/sheet-form";
 import type { WidgetInstance, WidgetInstanceInput } from "../types";
 import {
 	BUILTIN_WIDGETS,
@@ -277,201 +279,215 @@ export function WidgetConfigDialog({ open, onClose }: Props) {
 				]?.widgets.find((w) => w.kind === draft.widgetKind)
 			: BUILTIN_WIDGETS[draft.widgetKind]
 		: undefined;
+	const isMobile = useIsMobile();
 	const isTaskOutput =
 		draft?.serviceId !== null &&
 		services.find((s) => s.id === draft?.serviceId)?.service_type ===
 			"ssh_tasks";
 
+	// The draft body (Title/SortOrder/Enabled/config editor) is shared between
+	// the Dialog (desktop) and SheetForm (mobile). On mobile the inline
+	// Back/Save buttons are omitted because the SheetForm footer provides them.
+	const draftBody = draft ? (
+		<div className="flex flex-col gap-4">
+			<div className="grid grid-cols-1 gap-3 sm:grid-cols-2">
+				<Field label="Title" htmlFor="widget-title">
+					<Input
+						id="widget-title"
+						value={draft.title}
+						onChange={(e) => setDraft({ ...draft, title: e.target.value })}
+					/>
+				</Field>
+				<Field label="Sort order" htmlFor="widget-sort-order">
+					<Input
+						id="widget-sort-order"
+						type="number"
+						value={String(draft.sortOrder)}
+						onChange={(e) =>
+							setDraft({
+								...draft,
+								sortOrder: e.target.value === "" ? 0 : Number(e.target.value),
+							})
+						}
+					/>
+				</Field>
+			</div>
+			<div className="flex items-center gap-2">
+				<Switch
+					id="widget-enabled"
+					checked={draft.enabled}
+					onCheckedChange={(checked) =>
+						setDraft({ ...draft, enabled: checked })
+					}
+				/>
+				<Label htmlFor="widget-enabled">Enabled</Label>
+			</div>
+			<WidgetConfigEditor
+				binding={draftBinding}
+				isTaskOutput={!!isTaskOutput}
+				config={draft.config}
+				onChange={(config) => setDraft({ ...draft, config })}
+				tasks={tasks}
+			/>
+			{!isMobile ? (
+				<div className="flex justify-end gap-2">
+					<Button variant="outline" onClick={reset}>
+						Back
+					</Button>
+					<Button onClick={saveDraft} disabled={saveWidget.isPending}>
+						Save widget
+					</Button>
+				</div>
+			) : null}
+		</div>
+	) : (
+		<div className="flex flex-col gap-4">
+			{sortedInstances.length === 0 ? (
+				<Alert>
+					<AlertDescription>No widgets yet. Add one below.</AlertDescription>
+				</Alert>
+			) : (
+				<div className="flex flex-col gap-2">
+					{sortedInstances.map((instance, index) => {
+						const serviceName = instance.service_id
+							? services.find((s) => s.id === instance.service_id)?.name
+							: "Built-in";
+						return (
+							<div
+								key={instance.id}
+								className="flex items-center gap-2 rounded border p-2"
+							>
+								<div className="flex flex-1 flex-col gap-1">
+									<div className="flex items-center gap-2">
+										<span className="font-medium">{instance.title}</span>
+										<Badge variant="outline">
+											{bindingLabel(instance.service_id, instance.widget_kind)}
+										</Badge>
+										{serviceName ? (
+											<span className="text-xs text-muted-foreground">
+												{serviceName}
+											</span>
+										) : null}
+										{!instance.enabled ? (
+											<Badge variant="secondary">disabled</Badge>
+										) : null}
+									</div>
+								</div>
+								<div className="flex items-center gap-1">
+									<Button
+										variant="ghost"
+										size="icon"
+										className="h-8 w-8"
+										disabled={index === 0}
+										onClick={() => moveInstance(index, -1)}
+									>
+										<ChevronUp className="h-4 w-4" />
+									</Button>
+									<Button
+										variant="ghost"
+										size="icon"
+										className="h-8 w-8"
+										disabled={index === sortedInstances.length - 1}
+										onClick={() => moveInstance(index, 1)}
+									>
+										<ChevronDown className="h-4 w-4" />
+									</Button>
+									<Switch
+										checked={instance.enabled}
+										onCheckedChange={() => toggleEnabled(instance)}
+										aria-label={`Toggle ${instance.title}`}
+									/>
+									<Button
+										variant="ghost"
+										size="icon"
+										className="h-8 w-8"
+										onClick={() => startEdit(instance)}
+									>
+										<Pencil className="h-4 w-4" />
+									</Button>
+									<Button
+										variant="ghost"
+										size="icon"
+										className="h-8 w-8 text-destructive"
+										onClick={() => removeInstance(instance)}
+									>
+										<Trash2 className="h-4 w-4" />
+									</Button>
+								</div>
+							</div>
+						);
+					})}
+				</div>
+			)}
+
+			<div className="flex flex-col gap-2">
+				<p className="text-sm font-medium">Add widget</p>
+				<div className="flex flex-wrap gap-2">
+					{Object.values(BUILTIN_WIDGETS).map((b) => (
+						<Button
+							key={b.kind}
+							variant="outline"
+							size="sm"
+							onClick={() => startAddBuiltIn(b.kind)}
+						>
+							<Plus className="mr-1 h-3 w-3" />
+							{b.name}
+						</Button>
+					))}
+					{services
+						.filter((s) => s.enabled)
+						.flatMap((s) =>
+							(SERVICE_REGISTRY[s.service_type]?.widgets ?? []).map((w) => (
+								<Button
+									key={`${s.id}:${w.kind}`}
+									variant="outline"
+									size="sm"
+									onClick={() => startAddService(s.id, w.kind)}
+								>
+									<Plus className="mr-1 h-3 w-3" />
+									{w.name} · {s.name}
+								</Button>
+							)),
+						)}
+				</div>
+				<p className="text-xs text-muted-foreground">
+					Configure services on their service pages to unlock more widgets.
+				</p>
+			</div>
+		</div>
+	);
+
+	const dialogTitle = draft
+		? draft.id
+			? "Edit widget"
+			: "Add widget"
+		: "Dashboard widgets";
+
+	if (isMobile) {
+		return (
+			<SheetForm
+				open={open}
+				onOpenChange={(next) => {
+					if (!next) handleClose(next);
+				}}
+				title={dialogTitle}
+				onSave={draft ? saveDraft : () => handleClose(false)}
+				onCancel={draft ? reset : () => handleClose(false)}
+				saveLabel={draft ? "Save widget" : "Done"}
+				isPending={draft ? saveWidget.isPending : false}
+			>
+				<div className="flex flex-col gap-4">{draftBody}</div>
+			</SheetForm>
+		);
+	}
+
 	return (
 		<Dialog open={open} onOpenChange={handleClose}>
 			<DialogContent className="sm:max-w-2xl">
 				<DialogHeader>
-					<DialogTitle>
-						{draft
-							? draft.id
-								? "Edit widget"
-								: "Add widget"
-							: "Dashboard widgets"}
-					</DialogTitle>
+					<DialogTitle>{dialogTitle}</DialogTitle>
 				</DialogHeader>
-
-				{draft ? (
-					<div className="flex flex-col gap-4">
-						<div className="grid grid-cols-1 gap-3 sm:grid-cols-2">
-							<Field label="Title" htmlFor="widget-title">
-								<Input
-									id="widget-title"
-									value={draft.title}
-									onChange={(e) =>
-										setDraft({ ...draft, title: e.target.value })
-									}
-								/>
-							</Field>
-							<Field label="Sort order" htmlFor="widget-sort-order">
-								<Input
-									id="widget-sort-order"
-									type="number"
-									value={String(draft.sortOrder)}
-									onChange={(e) =>
-										setDraft({
-											...draft,
-											sortOrder:
-												e.target.value === "" ? 0 : Number(e.target.value),
-										})
-									}
-								/>
-							</Field>
-						</div>
-						<div className="flex items-center gap-2">
-							<Switch
-								id="widget-enabled"
-								checked={draft.enabled}
-								onCheckedChange={(checked) =>
-									setDraft({ ...draft, enabled: checked })
-								}
-							/>
-							<Label htmlFor="widget-enabled">Enabled</Label>
-						</div>
-						<WidgetConfigEditor
-							binding={draftBinding}
-							isTaskOutput={!!isTaskOutput}
-							config={draft.config}
-							onChange={(config) => setDraft({ ...draft, config })}
-							tasks={tasks}
-						/>
-						<div className="flex justify-end gap-2">
-							<Button variant="outline" onClick={reset}>
-								Back
-							</Button>
-							<Button onClick={saveDraft} disabled={saveWidget.isPending}>
-								Save widget
-							</Button>
-						</div>
-					</div>
-				) : (
-					<div className="flex flex-col gap-4">
-						{sortedInstances.length === 0 ? (
-							<Alert>
-								<AlertDescription>
-									No widgets yet. Add one below.
-								</AlertDescription>
-							</Alert>
-						) : (
-							<div className="flex flex-col gap-2">
-								{sortedInstances.map((instance, index) => {
-									const serviceName = instance.service_id
-										? services.find((s) => s.id === instance.service_id)?.name
-										: "Built-in";
-									return (
-										<div
-											key={instance.id}
-											className="flex items-center gap-2 rounded border p-2"
-										>
-											<div className="flex flex-1 flex-col gap-1">
-												<div className="flex items-center gap-2">
-													<span className="font-medium">{instance.title}</span>
-													<Badge variant="outline">
-														{bindingLabel(
-															instance.service_id,
-															instance.widget_kind,
-														)}
-													</Badge>
-													{serviceName ? (
-														<span className="text-xs text-muted-foreground">
-															{serviceName}
-														</span>
-													) : null}
-													{!instance.enabled ? (
-														<Badge variant="secondary">disabled</Badge>
-													) : null}
-												</div>
-											</div>
-											<div className="flex items-center gap-1">
-												<Button
-													variant="ghost"
-													size="icon"
-													className="h-8 w-8"
-													disabled={index === 0}
-													onClick={() => moveInstance(index, -1)}
-												>
-													<ChevronUp className="h-4 w-4" />
-												</Button>
-												<Button
-													variant="ghost"
-													size="icon"
-													className="h-8 w-8"
-													disabled={index === sortedInstances.length - 1}
-													onClick={() => moveInstance(index, 1)}
-												>
-													<ChevronDown className="h-4 w-4" />
-												</Button>
-												<Switch
-													checked={instance.enabled}
-													onCheckedChange={() => toggleEnabled(instance)}
-													aria-label={`Toggle ${instance.title}`}
-												/>
-												<Button
-													variant="ghost"
-													size="icon"
-													className="h-8 w-8"
-													onClick={() => startEdit(instance)}
-												>
-													<Pencil className="h-4 w-4" />
-												</Button>
-												<Button
-													variant="ghost"
-													size="icon"
-													className="h-8 w-8 text-destructive"
-													onClick={() => removeInstance(instance)}
-												>
-													<Trash2 className="h-4 w-4" />
-												</Button>
-											</div>
-										</div>
-									);
-								})}
-							</div>
-						)}
-
-						<div className="flex flex-col gap-2">
-							<p className="text-sm font-medium">Add widget</p>
-							<div className="flex flex-wrap gap-2">
-								{Object.values(BUILTIN_WIDGETS).map((b) => (
-									<Button
-										key={b.kind}
-										variant="outline"
-										size="sm"
-										onClick={() => startAddBuiltIn(b.kind)}
-									>
-										<Plus className="mr-1 h-3 w-3" />
-										{b.name}
-									</Button>
-								))}
-								{services
-									.filter((s) => s.enabled)
-									.flatMap((s) =>
-										(SERVICE_REGISTRY[s.service_type]?.widgets ?? []).map(
-											(w) => (
-												<Button
-													key={`${s.id}:${w.kind}`}
-													variant="outline"
-													size="sm"
-													onClick={() => startAddService(s.id, w.kind)}
-												>
-													<Plus className="mr-1 h-3 w-3" />
-													{w.name} · {s.name}
-												</Button>
-											),
-										),
-									)}
-							</div>
-							<p className="text-xs text-muted-foreground">
-								Configure services on their service pages to unlock more
-								widgets.
-							</p>
-						</div>
-					</div>
-				)}
+				{draftBody}
 			</DialogContent>
 		</Dialog>
 	);