Add quick-win tests for components and hooks

Adds tests for DifficultyIndicator, Toast, RollModeMenu, OverflowMenu,
useTheme, and useRulesEdition. Covers rendering, user interactions,
auto-dismiss timers, external store sync, and localStorage persistence.

Co-Authored-By: Claude Opus 4.6 (1M context) <noreply@anthropic.com>

apps/web/src/components/__tests__/toast.test.tsx

@@ -0,0 +1,68 @@
+// @vitest-environment jsdom
+import { cleanup, render, screen } from "@testing-library/react";
+import { userEvent } from "@testing-library/user-event";
+import { afterEach, beforeEach, describe, expect, it, vi } from "vitest";
+import { Toast } from "../toast.js";
+
+afterEach(cleanup);
+
+describe("Toast", () => {
+	it("renders message text", () => {
+		render(<Toast message="Hello" onDismiss={() => {}} />);
+		expect(screen.getByText("Hello")).toBeDefined();
+	});
+
+	it("renders progress bar when progress is provided", () => {
+		render(<Toast message="Loading" progress={0.5} onDismiss={() => {}} />);
+		const bar = document.body.querySelector("[style*='width']") as HTMLElement;
+		expect(bar).not.toBeNull();
+		expect(bar.style.width).toBe("50%");
+	});
+
+	it("does not render progress bar when progress is omitted", () => {
+		render(<Toast message="Done" onDismiss={() => {}} />);
+		const bar = document.body.querySelector("[style*='width']");
+		expect(bar).toBeNull();
+	});
+
+	it("calls onDismiss when close button is clicked", async () => {
+		const onDismiss = vi.fn();
+		render(<Toast message="Hi" onDismiss={onDismiss} />);
+
+		const toast = screen.getByText("Hi").closest("div");
+		const button = toast?.querySelector("button");
+		expect(button).not.toBeNull();
+		await userEvent.click(button as HTMLElement);
+
+		expect(onDismiss).toHaveBeenCalledOnce();
+	});
+
+	describe("auto-dismiss", () => {
+		beforeEach(() => {
+			vi.useFakeTimers();
+		});
+
+		afterEach(() => {
+			vi.useRealTimers();
+		});
+
+		it("auto-dismisses after specified timeout", () => {
+			const onDismiss = vi.fn();
+			render(
+				<Toast message="Auto" onDismiss={onDismiss} autoDismissMs={3000} />,
+			);
+
+			expect(onDismiss).not.toHaveBeenCalled();
+			vi.advanceTimersByTime(3000);
+			expect(onDismiss).toHaveBeenCalledOnce();
+		});
+
+		it("does not auto-dismiss when autoDismissMs is omitted", () => {
+			const onDismiss = vi.fn();
+			render(<Toast message="Stay" onDismiss={onDismiss} />);
+
+			vi.advanceTimersByTime(10000);
+			expect(onDismiss).not.toHaveBeenCalled();
+		});
+	});
+});