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,
@@ -277,34 +279,23 @@ 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";
 
-	return (
-		<Dialog open={open} onOpenChange={handleClose}>
-			<DialogContent className="sm:max-w-2xl">
-				<DialogHeader>
-					<DialogTitle>
-						{draft
-							? draft.id
-								? "Edit widget"
-								: "Add widget"
-							: "Dashboard widgets"}
-					</DialogTitle>
-				</DialogHeader>
-
-				{draft ? (
+	// 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 })
-									}
+						onChange={(e) => setDraft({ ...draft, title: e.target.value })}
 					/>
 				</Field>
 				<Field label="Sort order" htmlFor="widget-sort-order">
@@ -315,8 +306,7 @@ export function WidgetConfigDialog({ open, onClose }: Props) {
 						onChange={(e) =>
 							setDraft({
 								...draft,
-											sortOrder:
-												e.target.value === "" ? 0 : Number(e.target.value),
+								sortOrder: e.target.value === "" ? 0 : Number(e.target.value),
 							})
 						}
 					/>
@@ -339,6 +329,7 @@ export function WidgetConfigDialog({ open, onClose }: Props) {
 				onChange={(config) => setDraft({ ...draft, config })}
 				tasks={tasks}
 			/>
+			{!isMobile ? (
 				<div className="flex justify-end gap-2">
 					<Button variant="outline" onClick={reset}>
 						Back
@@ -347,14 +338,13 @@ export function WidgetConfigDialog({ open, onClose }: Props) {
 						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>
+					<AlertDescription>No widgets yet. Add one below.</AlertDescription>
 				</Alert>
 			) : (
 				<div className="flex flex-col gap-2">
@@ -371,10 +361,7 @@ export function WidgetConfigDialog({ open, onClose }: Props) {
 									<div className="flex items-center gap-2">
 										<span className="font-medium">{instance.title}</span>
 										<Badge variant="outline">
-														{bindingLabel(
-															instance.service_id,
-															instance.widget_kind,
-														)}
+											{bindingLabel(instance.service_id, instance.widget_kind)}
 										</Badge>
 										{serviceName ? (
 											<span className="text-xs text-muted-foreground">
@@ -450,8 +437,7 @@ export function WidgetConfigDialog({ open, onClose }: Props) {
 					{services
 						.filter((s) => s.enabled)
 						.flatMap((s) =>
-										(SERVICE_REGISTRY[s.service_type]?.widgets ?? []).map(
-											(w) => (
+							(SERVICE_REGISTRY[s.service_type]?.widgets ?? []).map((w) => (
 								<Button
 									key={`${s.id}:${w.kind}`}
 									variant="outline"
@@ -461,17 +447,47 @@ export function WidgetConfigDialog({ open, onClose }: Props) {
 									<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.
+					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>{dialogTitle}</DialogTitle>
+				</DialogHeader>
+				{draftBody}
 			</DialogContent>
 		</Dialog>
 	);

frontend/src/components/__tests__/WidgetConfigDialog.test.tsx

@@ -0,0 +1,53 @@
+import { describe, it, expect, beforeEach, vi } from "vitest";
+import { render, screen } from "@testing-library/react";
+import { WidgetConfigDialog } from "../WidgetConfigDialog";
+
+// jsdom has no window.matchMedia; default to desktop (matches: false).
+function setMatchMedia(matches: boolean) {
+	window.matchMedia = ((query: string) => ({
+		matches: query.includes("768") ? matches : false,
+		media: query,
+		onchange: null,
+		addEventListener: () => {},
+		removeEventListener: () => {},
+		addListener: () => {},
+		removeListener: () => {},
+		dispatchEvent: () => false,
+	})) as unknown as typeof window.matchMedia;
+}
+
+vi.mock("../../hooks/useWidgets", () => ({
+	useWidgetInstances: () => ({ data: [] }),
+	useSaveWidgetInstance: () => ({ mutateAsync: vi.fn(), isPending: false }),
+	useDeleteWidgetInstance: () => ({ mutateAsync: vi.fn(), isPending: false }),
+}));
+
+vi.mock("../../hooks/useServices", () => ({
+	useServiceInstances: () => ({ data: [] }),
+}));
+
+vi.mock("../../hooks/useSettings", () => ({
+	useTasks: () => ({ data: [] }),
+}));
+
+beforeEach(() => setMatchMedia(false));
+
+describe("WidgetConfigDialog (desktop)", () => {
+	it("renders a Dialog with the dashboard widgets title at md+", () => {
+		render(<WidgetConfigDialog open={true} onClose={() => {}} />);
+		expect(
+			screen.getByRole("heading", { name: "Dashboard widgets" }),
+		).toBeInTheDocument();
+	});
+});
+
+describe("WidgetConfigDialog (mobile SheetForm — slice 8)", () => {
+	beforeEach(() => setMatchMedia(true));
+
+	it("renders a SheetForm with the dashboard widgets title below md", () => {
+		render(<WidgetConfigDialog open={true} onClose={() => {}} />);
+		expect(screen.getByText("Dashboard widgets")).toBeInTheDocument();
+		// List mode footer: "Done" button closes.
+		expect(screen.getByRole("button", { name: "Done" })).toBeInTheDocument();
+	});
+});

frontend/src/pages/UsersPage.impl.tsx

@@ -40,6 +40,7 @@ import {
 	TooltipTrigger,
 } from "@/components/ui/tooltip";
 import { Sheet, SheetContent } from "@/components/ui/sheet";
+import { SheetForm } from "@/components/ui/sheet-form";
 import {
 	Table,
 	TableBody,
@@ -813,27 +814,10 @@ export function UsersPage() {
 				</SheetContent>
 			</Sheet>
 
-			<Dialog
-				open={composeOpen}
-				onOpenChange={(open) => {
-					if (!open) {
-						closeCompose();
-					}
-				}}
-			>
-				<DialogContent
-					className={cn(
-						"flex max-h-[90dvh] flex-col gap-0 overflow-hidden p-0 sm:max-w-2xl",
-						isComposeMobile &&
-							"inset-0 max-h-none max-w-none translate-x-0 translate-y-0 rounded-none",
-					)}
-				>
-					<DialogHeader className="gap-1 px-4 pt-4">
-						<DialogTitle className="pr-8">Message selected users</DialogTitle>
-						<DialogDescription className="sr-only">
-							Compose a message to the selected deliverable users.
-						</DialogDescription>
-					</DialogHeader>
+			{/* Compose dialog: SheetForm below md, Dialog at md+ (spec R4.1) */}
+			{(() => {
+				const composeBody = (
+					<>
 						{sendUserMessage.isPending ? (
 							<Progress value={100} className="animate-pulse" />
 						) : null}
@@ -842,7 +826,8 @@ export function UsersPage() {
 								<UIAlert variant="destructive">
 									<AlertDescription>
 										Unable to send message:{" "}
-									{(sendUserMessage.error as Error)?.message || "Unknown error"}
+										{(sendUserMessage.error as Error)?.message ||
+											"Unknown error"}
 									</AlertDescription>
 								</UIAlert>
 							) : null}
@@ -878,8 +863,8 @@ export function UsersPage() {
 
 							<UIAlert>
 								<AlertDescription>
-								{selectedRows.length} selected, {selectedDeliverableRows.length}{" "}
-								deliverable.
+									{selectedRows.length} selected,{" "}
+									{selectedDeliverableRows.length} deliverable.
 									{skippedRows.length
 										? ` ${skippedRows.length} will be skipped because they do not have a deliverable email address.`
 										: ""}
@@ -1017,6 +1002,53 @@ export function UsersPage() {
 								))}
 							</div>
 						</div>
+					</>
+				);
+
+				if (isMobile) {
+					return (
+						<SheetForm
+							open={composeOpen}
+							onOpenChange={(open) => {
+								if (!open) closeCompose();
+							}}
+							title="Message selected users"
+							onSave={handleSend}
+							onCancel={closeCompose}
+							isPending={sendUserMessage.isPending}
+							saveDisabled={!selectedDeliverableRows.length || !subject.trim()}
+							saveLabel="Send message"
+						>
+							<div className="flex flex-col gap-4">{composeBody}</div>
+						</SheetForm>
+					);
+				}
+
+				return (
+					<Dialog
+						open={composeOpen}
+						onOpenChange={(open) => {
+							if (!open) {
+								closeCompose();
+							}
+						}}
+					>
+						<DialogContent
+							className={cn(
+								"flex max-h-[90dvh] flex-col gap-0 overflow-hidden p-0 sm:max-w-2xl",
+								isComposeMobile &&
+									"inset-0 max-h-none max-w-none translate-x-0 translate-y-0 rounded-none",
+							)}
+						>
+							<DialogHeader className="gap-1 px-4 pt-4">
+								<DialogTitle className="pr-8">
+									Message selected users
+								</DialogTitle>
+								<DialogDescription className="sr-only">
+									Compose a message to the selected deliverable users.
+								</DialogDescription>
+							</DialogHeader>
+							{composeBody}
 							<DialogFooter className="m-0 border-t p-4">
 								<UiButton variant="ghost" onClick={closeCompose}>
 									Cancel
@@ -1036,6 +1068,8 @@ export function UsersPage() {
 							</DialogFooter>
 						</DialogContent>
 					</Dialog>
+				);
+			})()}
 		</div>
 	);
 }

frontend/src/pages/__tests__/UsersPage.test.tsx

@@ -286,7 +286,7 @@ describe("UsersPage (slice 6b — compose dialog formatting actions)", () => {
 	});
 });
 
-	describe("UsersPage (mobile card layout — slice 5)", () => {
+describe("UsersPage (mobile card layout — slice 5)", () => {
 	beforeEach(() => {
 		window.matchMedia = ((query: string) => ({
 			matches: query.includes("768"),
@@ -342,4 +342,35 @@ describe("UsersPage (slice 6b — compose dialog formatting actions)", () => {
 		// drawer opens via a card-body tap, not via the checkbox.
 		expect(screen.queryByTestId("session-panel-stub")).not.toBeInTheDocument();
 	});
+
+	it("renders compose in a SheetForm below md with send button", async () => {
+		users = [
+			userFixture({
+				jellyfin_id: "u1",
+				display_name: "Alice",
+				email: "alice@example.com",
+			}),
+		];
+		render(
+			<TooltipProvider>
+				<UsersPage />
+			</TooltipProvider>,
+		);
+
+		// Select the deliverable user via the mobile card checkbox.
+		await userEvent.click(
+			screen.getByRole("checkbox", { name: /Select Alice/i }),
+		);
+		await userEvent.click(
+			screen.getByRole("button", { name: "Message selected" }),
+		);
+
+		// On mobile, compose opens in a SheetForm (not a Dialog). The SheetForm
+		// header carries the title and the footer carries the Send button.
+		expect(screen.getByText("Message selected users")).toBeInTheDocument();
+		expect(
+			screen.getByRole("button", { name: "Send message" }),
+		).toBeInTheDocument();
+		expect(screen.getByLabelText("Subject")).toBeInTheDocument();
+	});
 });