test(geschichte): replace waitForDebounce sleep with retrying locator waits (#795)

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

frontend/src/lib/geschichte/StoryDocumentPanel.svelte.spec.ts

@@ -4,8 +4,6 @@ import { page, userEvent } from 'vitest/browser';
 import { m } from '$lib/paraglide/messages.js';
 import StoryDocumentPanel from './StoryDocumentPanel.svelte';
 
-const waitForDebounce = () => new Promise((r) => setTimeout(r, 350));
-
 const docSummary = (id: string, title: string) => ({
 	id,
 	title,
@@ -79,7 +77,7 @@ const defaultProps = (overrides: Record<string, unknown> = {}) => ({
 
 async function addViaPicker(title: RegExp) {
 	await userEvent.fill(page.getByRole('combobox'), 'Brief');
-	await waitForDebounce();
+	await expect.element(page.getByText(title)).toBeInTheDocument();
 	await userEvent.click(page.getByText(title));
 }
 
@@ -160,7 +158,7 @@ describe('StoryDocumentPanel — add', () => {
 		);
 
 		await userEvent.fill(page.getByRole('combobox'), 'Brief');
-		await waitForDebounce();
+		await expect.element(page.getByRole('option')).toBeInTheDocument();
 
 		const option = document.querySelector('[role="listbox"] [role="option"]');
 		expect(option?.getAttribute('aria-disabled')).toBe('true');