admin: group sources and safe search become rac checkboxes

the assigned sources list is a rac checkboxgroup and safe search uses the same drawn checkbox, extracted to a shared ui component with grouped and standalone modes enforced by a discriminated union. the label carries a 44px pointer-target floor on both axes, the focus ring is driven from rac's focus-visible state and guarded by a test, and toggleSource is gone because the group hands back the whole set.

admin/src/ui/Checkbox.test.tsx

@@ -0,0 +1,92 @@
+import { act, fireEvent, render, screen, within } from "@testing-library/react";
+import Checkbox, { CheckboxGroup } from "./Checkbox";
+
+/**
+ * The drawn box, which is the label's one child that does not hold the hidden
+ * input. StyleX compiles to class names and jsdom loads no stylesheet, so the
+ * class list is the only place the composed ring is observable.
+ */
+function indicator(input: HTMLElement): HTMLElement {
+	const label = input.closest("label") as HTMLElement;
+	const spans = [...label.querySelectorAll("span")];
+	const box = spans.find((span) => !span.contains(input));
+	if (box === undefined) throw new Error("the checkbox drew no indicator");
+	return box;
+}
+
+test("a standalone checkbox reports its state and reads its label as its name", () => {
+	const onChange = vi.fn();
+	render(
+		<Checkbox isSelected onChange={onChange}>
+			Safe search
+		</Checkbox>,
+	);
+
+	const box = screen.getByRole("checkbox", { name: "Safe search" }) as HTMLInputElement;
+	expect(box.checked).toBe(true);
+
+	fireEvent.click(box);
+	// The caller owns the state, so the box reports the value it would move to
+	// rather than moving there itself.
+	expect(onChange).toHaveBeenCalledWith(false);
+});
+
+test("a disabled checkbox keeps its state on screen but takes no input", () => {
+	render(
+		<Checkbox isSelected isDisabled onChange={vi.fn()}>
+			Safe search
+		</Checkbox>,
+	);
+
+	const box = screen.getByRole("checkbox", { name: "Safe search" }) as HTMLInputElement;
+	expect(box.checked).toBe(true);
+	// The disabled input is the whole guard: a browser fires no click on one, and
+	// it is out of the tab order. Clicking it here would prove nothing either way,
+	// because `fireEvent` dispatches straight at the node and skips that check.
+	expect(box.disabled).toBe(true);
+});
+
+test("keyboard focus composes the ring onto the drawn box", () => {
+	render(
+		<Checkbox isSelected={false} onChange={vi.fn()}>
+			Ads
+		</Checkbox>,
+	);
+
+	const input = screen.getByRole("checkbox", { name: "Ads" });
+	const box = indicator(input);
+	const idle = box.className.split(" ");
+	expect(input.closest("label")?.getAttribute("data-focus-visible")).toBeNull();
+
+	// React Aria only calls focus visible after the modality is keyboard, which
+	// is why a bare focus() is not enough to raise the ring.
+	act(() => {
+		fireEvent.keyDown(document.body, { key: "Tab" });
+		input.focus();
+	});
+
+	expect(input.closest("label")?.getAttribute("data-focus-visible")).toBe("true");
+	const ringed = box.className.split(" ");
+	// The box gained classes it did not have: the ring is composed onto it, not
+	// merely reported by React Aria on the root.
+	expect(ringed.length).toBeGreaterThan(idle.length);
+	expect(idle.every((name) => ringed.includes(name))).toBe(true);
+});
+
+test("inside a group the group owns the selection, and the group carries the name", () => {
+	const onChange = vi.fn();
+	render(
+		<CheckboxGroup aria-label="Assigned sources" value={["1"]} onChange={onChange}>
+			<Checkbox value="1">Ads</Checkbox>
+			<Checkbox value="2">Trackers</Checkbox>
+		</CheckboxGroup>,
+	);
+
+	const group = screen.getByRole("group", { name: "Assigned sources" });
+	expect((within(group).getByRole("checkbox", { name: "Ads" }) as HTMLInputElement).checked).toBe(true);
+	expect((within(group).getByRole("checkbox", { name: "Trackers" }) as HTMLInputElement).checked).toBe(false);
+
+	// The group reports the whole set, not the box that moved.
+	fireEvent.click(within(group).getByRole("checkbox", { name: "Trackers" }));
+	expect(onChange).toHaveBeenCalledWith(["1", "2"]);
+});