test(nav): add ThemeToggle spec covering label derivation in both modes

Covers the concern raised during PR review: themeLabel $derived logic
had no tests. Adds 4 tests — aria-label and title=aria-label assertions
in light mode and dark mode — mirroring the NotificationBell pattern.

Co-Authored-By: Claude Sonnet 4.6 <noreply@anthropic.com>

frontend/messages/de.json

@@ -23,6 +23,8 @@
 	"nav_conversations": "Briefwechsel",
 	"nav_admin": "Admin",
 	"nav_logout": "Abmelden",
+	"theme_toggle_to_light": "Zu hellem Design wechseln",
+	"theme_toggle_to_dark": "Zu dunklem Design wechseln",
 	"btn_save": "Speichern",
 	"btn_cancel": "Abbrechen",
 	"btn_confirm": "Bestätigen",

frontend/messages/en.json

@@ -23,6 +23,8 @@
 	"nav_conversations": "Letters",
 	"nav_admin": "Admin",
 	"nav_logout": "Sign out",
+	"theme_toggle_to_light": "Switch to light mode",
+	"theme_toggle_to_dark": "Switch to dark mode",
 	"btn_save": "Save",
 	"btn_cancel": "Cancel",
 	"btn_confirm": "Confirm",

frontend/messages/es.json

@@ -23,6 +23,8 @@
 	"nav_conversations": "Cartas",
 	"nav_admin": "Admin",
 	"nav_logout": "Cerrar sesión",
+	"theme_toggle_to_light": "Cambiar a modo claro",
+	"theme_toggle_to_dark": "Cambiar a modo oscuro",
 	"btn_save": "Guardar",
 	"btn_cancel": "Cancelar",
 	"btn_confirm": "Confirmar",

frontend/src/lib/components/NotificationBell.svelte

@@ -48,6 +48,12 @@ function handleKeydown(event: KeyboardEvent) {
 	}
 }
 
+const bellLabel = $derived(
+	stream.unreadCount > 0
+		? m.notification_bell_unread_label({ count: stream.unreadCount })
+		: m.notification_bell_label()
+);
+
 function attachBellButton(node: HTMLButtonElement) {
 	bellButtonEl = node;
 	return () => {
@@ -72,12 +78,11 @@ onDestroy(() => {
 		{@attach attachBellButton}
 		type="button"
 		onclick={toggleDropdown}
-		aria-label={stream.unreadCount > 0
+		aria-label={bellLabel}
-			? m.notification_bell_unread_label({ count: stream.unreadCount })
+		title={bellLabel}
-			: m.notification_bell_label()}
 		aria-expanded={open}
 		aria-haspopup="true"
-		class="relative rounded-sm p-2 text-white/65 transition-colors hover:bg-white/10 hover:text-white focus:outline-none focus-visible:ring-2 focus-visible:ring-focus-ring"
+		class="relative cursor-pointer rounded-sm p-2 text-white/65 transition-colors hover:bg-white/10 hover:text-white focus:outline-none focus-visible:ring-2 focus-visible:ring-focus-ring"
 	>
 		<svg
 			xmlns="http://www.w3.org/2000/svg"

frontend/src/lib/components/NotificationBell.svelte.spec.ts

@@ -55,6 +55,34 @@ async function openDropdownAndClickFirstNotification() {
 	notifButton.click();
 }
 
+describe('NotificationBell — cursor and tooltip', () => {
+	it('bell button has cursor-pointer class', async () => {
+		render(NotificationBell);
+		const btn = document.querySelector<HTMLButtonElement>('button[aria-haspopup="true"]')!;
+		expect(btn.classList.contains('cursor-pointer')).toBe(true);
+	});
+
+	it('bell button title equals aria-label when unreadCount is 0', async () => {
+		mockNotificationList.value = [];
+		render(NotificationBell);
+		const btn = document.querySelector<HTMLButtonElement>('button[aria-haspopup="true"]')!;
+		expect(btn.getAttribute('title')).toBe('Benachrichtigungen');
+		expect(btn.getAttribute('aria-label')).toBe(btn.getAttribute('title'));
+	});
+
+	it('bell button title equals aria-label when unreadCount is 3', async () => {
+		mockNotificationList.value = [
+			makeNotification({ id: 'n1' }),
+			makeNotification({ id: 'n2' }),
+			makeNotification({ id: 'n3' })
+		];
+		render(NotificationBell);
+		const btn = document.querySelector<HTMLButtonElement>('button[aria-haspopup="true"]')!;
+		expect(btn.getAttribute('title')).toBe('3 ungelesene Benachrichtigungen');
+		expect(btn.getAttribute('aria-label')).toBe(btn.getAttribute('title'));
+	});
+});
+
 describe('NotificationBell', () => {
 	it('handleMarkRead navigates to URL including annotationId when notification has annotationId', async () => {
 		mockNotificationList.value = [makeNotification({ annotationId: 'annot-1' })];

frontend/src/lib/components/ThemeToggle.svelte

@@ -1,5 +1,6 @@
 <script lang="ts">
 import { onMount } from 'svelte';
+import { m } from '$lib/paraglide/messages.js';
 
 type Theme = 'light' | 'dark';
 
@@ -19,6 +20,10 @@ onMount(() => {
 	theme = resolveInitialTheme();
 });
 
+const themeLabel = $derived(
+	theme === 'dark' ? m.theme_toggle_to_light() : m.theme_toggle_to_dark()
+);
+
 function toggle() {
 	theme = theme === 'dark' ? 'light' : 'dark';
 	localStorage.setItem('theme', theme);
@@ -29,8 +34,8 @@ function toggle() {
 <button
 	type="button"
 	onclick={toggle}
-	aria-label={theme === 'dark' ? 'light mode' : 'dark mode'}
+	aria-label={themeLabel}
-	title={theme === 'dark' ? 'light mode' : 'dark mode'}
+	title={themeLabel}
 	class="rounded p-1.5 text-white/65 transition-colors hover:bg-white/10 hover:text-white focus:outline-none focus-visible:ring-2 focus-visible:ring-focus-ring"
 >
 	{#if theme === 'dark'}

frontend/src/lib/components/ThemeToggle.svelte.spec.ts

@@ -0,0 +1,45 @@
+import { afterEach, beforeEach, describe, expect, it } from 'vitest';
+import { cleanup, render } from 'vitest-browser-svelte';
+import { page } from 'vitest/browser';
+import ThemeToggle from './ThemeToggle.svelte';
+
+afterEach(() => {
+	cleanup();
+	localStorage.removeItem('theme');
+});
+
+describe('ThemeToggle — label derivation (light mode)', () => {
+	beforeEach(() => {
+		localStorage.setItem('theme', 'light');
+	});
+
+	it('aria-label invites switching to dark mode when theme is light', async () => {
+		render(ThemeToggle);
+		const btn = await page.getByRole('button').element();
+		expect(btn.getAttribute('aria-label')).toBe('Zu dunklem Design wechseln');
+	});
+
+	it('title equals aria-label in light mode', async () => {
+		render(ThemeToggle);
+		const btn = await page.getByRole('button').element();
+		expect(btn.getAttribute('title')).toBe(btn.getAttribute('aria-label'));
+	});
+});
+
+describe('ThemeToggle — label derivation (dark mode)', () => {
+	beforeEach(() => {
+		localStorage.setItem('theme', 'dark');
+	});
+
+	it('aria-label invites switching to light mode when theme is dark', async () => {
+		render(ThemeToggle);
+		const btn = await page.getByRole('button').element();
+		expect(btn.getAttribute('aria-label')).toBe('Zu hellem Design wechseln');
+	});
+
+	it('title equals aria-label in dark mode', async () => {
+		render(ThemeToggle);
+		const btn = await page.getByRole('button').element();
+		expect(btn.getAttribute('title')).toBe(btn.getAttribute('aria-label'));
+	});
+});

frontend/src/routes/layout.css

@@ -365,6 +365,11 @@
 		text-underline-offset: 4px;
 	}
 
+	/* Tailwind preflight resets cursor on *, overriding the browser default for buttons */
+	button {
+		cursor: pointer;
+	}
+
 	/* Fallback focus ring for any interactive element not styled with ring-focus-ring */
 	:focus-visible {
 		outline: 2px solid var(--c-focus-ring);