Mobile Media table: stacked cards + mobile pagination (Slice 3)

Below md, the Media DataTable renders as MobileCardRow cards: title as
primary, plus size/HDR/library/year (3-5 fields, null-safe). Card tap
navigates to /files?path=... (same handleRowClick as desktop). The TanStack
column-visibility toggle is absent below md (the card picks the fields).

Pagination is preserved via a standalone MediaMobilePagination component
that mirrors DataTablePagination semantics (rows count, page-size select,
page indicator, prev/next with correct disabled states) off the raw
PaginationState. The duplication is flagged tech debt -- extracting a shared
TablePagination is a follow-up, out of scope for this slice.

Desktop (md+) is byte-for-byte identical: the isMobile===false branch
renders the same DataTable with the same props. enableRowSelection state is
vestigial (no batch consumer on either path); navigation is the correct
primary mobile interaction.

Tests: 5 new covering mobile cards + hidden column toggle + pagination +
card-tap navigation, and desktop DataTable + column toggle. matchMedia
mocked per-breakpoint. 94 tests pass; lint/build green.

Refs openspec/changes/mobile-responsive-parity/ (spec R3, tasks slice 3).

frontend/src/pages/Media.tsx

@@ -9,6 +9,10 @@ import type {
 } from "@tanstack/react-table";
 
 import { DataTable } from "@/components/ui/data-table";
+import {
+	MobileCardRow,
+	type MobileCardField,
+} from "@/components/ui/mobile-card";
 import { Alert, AlertDescription } from "@/components/ui/alert";
 import { Button } from "@/components/ui/button";
 import { Card, CardContent } from "@/components/ui/card";
@@ -31,6 +35,7 @@ import {
 	useForceStopBuildIndex,
 } from "../hooks/useMedia";
 import { usePersistentState } from "../hooks/usePersistentState";
+import { useIsMobile } from "../hooks/useIsMobile";
 import type { MediaItem } from "../types";
 import { useServiceInstances } from "../hooks/useServices";
 import { useCounts, useLibraries } from "../hooks/useDashboard";
@@ -75,6 +80,116 @@ function getMediaRowId(row: MediaItem): string {
 	return row.path;
 }
 
+// Mobile card fields (spec R3.2): the card picks the 3-5 most important fields.
+// Title is the primary identifier; size/HDR/library/year give the at-a-glance
+// tech + context info a user scanning the library on a phone needs. Runtime,
+// bitrate, resolution, codec etc. live on the desktop table only.
+const mediaCardFields: MobileCardField<MediaItem>[] = [
+	{ key: "title", label: "Title", render: (r) => r.title, primary: true },
+	{ key: "size", label: "Size", render: (r) => r.size || "-" },
+	{
+		key: "hdr",
+		label: "HDR",
+		render: (r) => r.hdr || "-",
+	},
+	{ key: "library", label: "Library", render: (r) => r.library || "-" },
+	{
+		key: "year",
+		label: "Year",
+		render: (r) => (r.year != null ? String(r.year) : "-"),
+	},
+];
+
+// Standalone pagination for the mobile card layout. The DataTable renders its
+// own pagination internally; this mirrors that UI (rows count, page-size
+// select, page indicator, prev/next) but works off the raw pagination state
+// instead of a TanStack table instance. See spec R3.3.
+function MediaMobilePagination({
+	pageIndex,
+	pageSize,
+	pageSizeOptions,
+	totalRows,
+	pageCount,
+	onPaginationChange,
+}: {
+	pageIndex: number;
+	pageSize: number;
+	pageSizeOptions: number[];
+	totalRows: number;
+	pageCount: number;
+	onPaginationChange: OnChangeFn<PaginationState>;
+}) {
+	return (
+		<div className="flex flex-wrap items-center justify-between gap-3 p-4 text-sm">
+			<div className="text-muted-foreground">
+				{`${totalRows} row${totalRows === 1 ? "" : "s"}`}
+			</div>
+			<div className="flex items-center gap-3">
+				<div className="flex items-center gap-1.5">
+					<span className="text-muted-foreground">Rows per page</span>
+					<Select
+						value={String(pageSize)}
+						onValueChange={(value) =>
+							onPaginationChange(() => ({
+								pageIndex: 0,
+								pageSize: Number(value),
+							}))
+						}
+					>
+						<SelectTrigger
+							size="sm"
+							className="w-[70px]"
+							aria-label="Rows per page"
+						>
+							<SelectValue />
+						</SelectTrigger>
+						<SelectContent>
+							{pageSizeOptions.map((option) => (
+								<SelectItem key={option} value={String(option)}>
+									{option}
+								</SelectItem>
+							))}
+						</SelectContent>
+					</Select>
+				</div>
+				<span className="text-muted-foreground">
+					Page {pageIndex + 1} of {pageCount}
+				</span>
+				<div className="flex items-center gap-1">
+					<Button
+						variant="outline"
+						size="sm"
+						onClick={() =>
+							onPaginationChange((prev) => ({
+								...prev,
+								pageIndex: Math.max(0, prev.pageIndex - 1),
+							}))
+						}
+						disabled={pageIndex <= 0}
+						aria-label="Previous page"
+					>
+						Previous
+					</Button>
+					<Button
+						variant="outline"
+						size="sm"
+						onClick={() =>
+							onPaginationChange((prev) => ({
+								...prev,
+								pageIndex: prev.pageIndex + 1,
+							}))
+						}
+						disabled={pageIndex >= pageCount - 1}
+						aria-label="Next page"
+					>
+						Next
+					</Button>
+				</div>
+			</div>
+		</div>
+	);
+}
+
 const MEDIA_TAB_STATE_KEY = "manage.media.tabState";
 const SMALL_BREAKPOINT = "(max-width: 900px)";
 // Mirrors the pre-rework DataGrid `columnVisibilityModel` mobile override.
@@ -178,6 +293,7 @@ export function Media() {
 	const navigate = useNavigate();
 	const [searchParams, setSearchParams] = useSearchParams();
 	const isSmall = usePrefersSmallScreen();
+	const isMobile = useIsMobile();
 	const { data: jellyfinServices = [] } = useServiceInstances("jellyfin");
 	const selectedServiceId =
 		searchParams.get("jellyfin_service_id") ||
@@ -532,7 +648,29 @@ export function Media() {
 				</p>
 			)}
 
-			{status?.exists && (
+			{status?.exists &&
+				(isMobile ? (
+					<div className="rounded-lg border bg-card">
+						<div className="p-4">
+							<MobileCardRow
+								rows={queryResult?.items ?? []}
+								fields={mediaCardFields}
+								getRowId={getMediaRowId}
+								onRowClick={handleRowClick}
+							/>
+						</div>
+						{queryResult && (
+							<MediaMobilePagination
+								pageIndex={pageIndex}
+								pageSize={pageSize}
+								pageSizeOptions={[50, 100, 200]}
+								totalRows={total}
+								pageCount={totalPages}
+								onPaginationChange={handlePaginationChange}
+							/>
+						)}
+					</div>
+				) : (
 					<div className="rounded-lg border bg-card">
 						<DataTable
 							columns={mediaColumns}
@@ -558,7 +696,7 @@ export function Media() {
 							}
 						/>
 					</div>
-			)}
+				))}
 		</div>
 	);
 }

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

@@ -129,7 +129,11 @@ vi.mock("../../hooks/useDashboard", () => ({
 
 // usePersistentState reads/writes localStorage; clear between tests so the
 // offset/pageSize/columnVisibility state never leaks across cases.
+// matchMedia must be stubbed so useIsMobile (md:768px) and usePrefersSmallScreen
+// (900px) resolve without TypeError in jsdom. Default to desktop (matches:false)
+// so the DataTable path renders by default; mobile tests override.
 beforeEach(() => {
+	setMatchMedia(false);
 	window.localStorage.clear();
 	navigate.mockClear();
 	status = statusFixture();
@@ -152,6 +156,30 @@ beforeEach(() => {
 	};
 });
 
+/** Stub window.matchMedia so useIsMobile / usePrefersSmallScreen resolve in jsdom. */
+function setMatchMedia(matches: boolean) {
+	const listeners: ((e: MediaQueryListEvent) => void)[] = [];
+	window.matchMedia = vi.fn().mockImplementation((query: string) => ({
+		matches: query.includes("768") ? matches : false,
+		media: query,
+		onchange: null,
+		addEventListener: (
+			_evt: string,
+			listener: (e: MediaQueryListEvent) => void,
+		) => listeners.push(listener),
+		removeEventListener: (
+			_evt: string,
+			listener: (e: MediaQueryListEvent) => void,
+		) => {
+			const idx = listeners.indexOf(listener);
+			if (idx >= 0) listeners.splice(idx, 1);
+		},
+		addListener: () => {},
+		removeListener: () => {},
+		dispatchEvent: () => false,
+	}));
+}
+
 describe("Media (slice 7b — TanStack DataTable + server-driven pagination)", () => {
 	it("exposes exactly the 15 locked toggleable columns", async () => {
 		render(<Media />);
@@ -261,3 +289,68 @@ describe("Media (slice 7b — TanStack DataTable + server-driven pagination)", (
 		).toBeInTheDocument();
 	});
 });
+
+describe("Media (mobile card layout — slice 3)", () => {
+	it("renders cards with the title as primary below md", () => {
+		setMatchMedia(true);
+		render(<Media />);
+
+		// Card titles render (primary field).
+		expect(screen.getByText("Inception")).toBeInTheDocument();
+		expect(screen.getByText("Matrix")).toBeInTheDocument();
+
+		// Card field labels render (at least once per row).
+		expect(screen.getAllByText("Size").length).toBeGreaterThanOrEqual(2);
+		expect(screen.getAllByText("HDR").length).toBeGreaterThanOrEqual(2);
+		expect(screen.getAllByText("Library").length).toBeGreaterThanOrEqual(2);
+		expect(screen.getAllByText("Year").length).toBeGreaterThanOrEqual(2);
+
+		// Desktop table headers do NOT render on mobile.
+		expect(screen.queryByRole("columnheader", { name: "Title" })).toBeNull();
+		expect(screen.queryByRole("columnheader", { name: "Bitrate" })).toBeNull();
+	});
+
+	it("hides the column-visibility toggle below md", () => {
+		setMatchMedia(true);
+		render(<Media />);
+
+		expect(screen.queryByRole("button", { name: /Columns/ })).toBeNull();
+	});
+
+	it("renders pagination controls below the cards on mobile", () => {
+		setMatchMedia(true);
+		render(<Media />);
+
+		expect(screen.getByText("2 rows")).toBeInTheDocument();
+		expect(screen.getAllByText(/Page 1 of 1/).length).toBeGreaterThan(0);
+		expect(
+			screen.getByRole("button", { name: "Previous page" }),
+		).toBeDisabled();
+		expect(
+			screen.getByRole("button", { name: "Next page" }),
+		).toBeInTheDocument();
+	});
+
+	it("navigates to the file browser when a card is tapped on mobile", async () => {
+		setMatchMedia(true);
+		render(<Media />);
+
+		await userEvent.click(screen.getByText("Inception"));
+
+		expect(navigate).toHaveBeenCalledTimes(1);
+		expect(navigate).toHaveBeenCalledWith(
+			`/files?path=${encodeURIComponent("/media/movies/Inception.mkv")}`,
+		);
+	});
+
+	it("renders the DataTable (not cards) at desktop width", () => {
+		render(<Media />);
+
+		// Desktop column headers render.
+		expect(
+			screen.getByRole("columnheader", { name: "Title" }),
+		).toBeInTheDocument();
+		// Column-visibility toggle is present.
+		expect(screen.getByRole("button", { name: /Columns/ })).toBeInTheDocument();
+	});
+});