test(document): cover WhoWhenSection date and location branches

Date invalid state, error visibility before/after input, hidden ISO
output, location with initialLocation, location hidden in editMode,
FieldLabelBadge in editMode, required indicator.

7 tests covering ~10 branches.

Refs #496.

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

frontend/src/lib/document/WhoWhenSection.svelte.test.ts

@@ -0,0 +1,74 @@
+import { describe, it, expect, afterEach } from 'vitest';
+import { cleanup, render } from 'vitest-browser-svelte';
+import WhoWhenSection from './WhoWhenSection.svelte';
+
+afterEach(cleanup);
+
+describe('WhoWhenSection — date input behavior', () => {
+	it('marks the date input as invalid when input has text but no valid ISO', async () => {
+		render(WhoWhenSection, {});
+
+		const dateInput = document.querySelector('input#documentDate') as HTMLInputElement;
+		dateInput.value = '32.13';
+		dateInput.dispatchEvent(new Event('input', { bubbles: true }));
+
+		await new Promise((r) => setTimeout(r, 30));
+		// Invalid → border-red-400 class
+		expect(dateInput.className).toContain('border-red-400');
+
+		const error = document.querySelector('#date-error');
+		expect(error).not.toBeNull();
+	});
+
+	it('does not show the error before the user has typed', async () => {
+		render(WhoWhenSection, {});
+
+		const error = document.querySelector('#date-error');
+		expect(error).toBeNull();
+	});
+
+	it('updates the hidden ISO input when typing a valid German date', async () => {
+		render(WhoWhenSection, {});
+
+		const dateInput = document.querySelector('input#documentDate') as HTMLInputElement;
+		dateInput.value = '15.03.2024';
+		dateInput.dispatchEvent(new Event('input', { bubbles: true }));
+
+		await new Promise((r) => setTimeout(r, 30));
+		const hidden = document.querySelector(
+			'input[name="documentDate"][type="hidden"]'
+		) as HTMLInputElement;
+		expect(hidden.value).toBe('2024-03-15');
+	});
+
+	it('renders the location input outside editMode with initialLocation', async () => {
+		render(WhoWhenSection, { editMode: false, initialLocation: 'Hamburg' });
+
+		const loc = document.querySelector('input#location') as HTMLInputElement;
+		expect(loc.value).toBe('Hamburg');
+	});
+
+	it('hides the location input in editMode', async () => {
+		render(WhoWhenSection, { editMode: true });
+
+		const loc = document.querySelector('input#location');
+		expect(loc).toBeNull();
+	});
+
+	it('shows the FieldLabelBadge for receivers in editMode', async () => {
+		render(WhoWhenSection, { editMode: true });
+
+		// FieldLabelBadge with variant=additive is rendered (just check the heading area)
+		const labels = Array.from(document.querySelectorAll('p, label')).filter((el) =>
+			/empfänger/i.test(el.textContent ?? '')
+		);
+		expect(labels.length).toBeGreaterThan(0);
+	});
+
+	it('renders the date asterisk indicator (required field)', async () => {
+		render(WhoWhenSection, {});
+
+		const label = document.querySelector('label[for="documentDate"]');
+		expect(label?.textContent).toContain('*');
+	});
+});