test(stammbaum): mobile visual + structural e2e at 320/414/768 (#692)

VISUAL-gated screenshots of the first-load affordance + control cluster at
each width and the bottom-sheet-open state at 414px, plus always-on structural
assertions. New snapshots; the #361 desktop baselines are untouched. Baselines
regenerate in CI via --update-snapshots.

Co-Authored-By: Claude Opus 4.8 <noreply@anthropic.com>

frontend/e2e/stammbaum-mobile.visual.spec.ts

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+import { test, expect } from '@playwright/test';
+
+// Visual + structural coverage for the #692 mobile read path (pan/zoom/fit,
+// first-load affordance, bottom-sheet person panel).
+//
+// Snapshot assertions are gated on VISUAL=1 because they need pre-captured
+// baselines — regenerate in CI with `playwright test --update-snapshots` after
+// intentional UI changes. Structural assertions run unconditionally. The whole
+// suite is also subject to the project-wide Chromium-in-CI gate (#363); it
+// captures new snapshots rather than replacing the #361 desktop baselines.
+const VISUAL = process.env.VISUAL === '1';
+
+const WIDTHS = [320, 414, 768] as const;
+
+test.describe('Stammbaum — mobile read path (#692)', () => {
+	// Touch emulation so the canvas reports pointer:coarse and the first-load
+	// affordance appears; reduced-motion is already forced project-wide.
+	test.use({ hasTouch: true, isMobile: true });
+
+	for (const width of WIDTHS) {
+		test(`affordance + controls render at ${width}px`, async ({ page }) => {
+			await page.setViewportSize({ width, height: 720 });
+			await page.addInitScript(() => localStorage.removeItem('stammbaumAffordanceDismissedAt'));
+			await page.goto('/stammbaum');
+			await expect(page.getByRole('heading', { name: 'Stammbaum' })).toBeVisible();
+
+			const empty = page.getByRole('heading', { name: 'Noch keine Familienmitglieder' });
+			if (await empty.isVisible().catch(() => false)) {
+				test.skip(true, 'no seeded family tree in this environment');
+			}
+
+			// Bottom-right control cluster with the fit-to-screen affordance.
+			await expect(page.getByTestId('fit-to-screen')).toBeVisible();
+			// First-load interactive hint (touch only).
+			await expect(page.getByRole('status')).toBeVisible();
+
+			if (VISUAL) {
+				await expect(page).toHaveScreenshot(`stammbaum-affordance-${width}.png`, {
+					animations: 'disabled'
+				});
+			}
+		});
+	}
+
+	test('bottom sheet opens on node tap at 414px and preserves the canvas', async ({ page }) => {
+		await page.setViewportSize({ width: 414, height: 720 });
+		await page.goto('/stammbaum');
+		await expect(page.getByRole('heading', { name: 'Stammbaum' })).toBeVisible();
+
+		const node = page.locator('svg[aria-label="Stammbaum"] g[role="button"]').first();
+		if ((await node.count()) === 0) test.skip(true, 'no seeded nodes to tap');
+
+		await node.tap();
+		const sheet = page.getByRole('dialog');
+		await expect(sheet).toBeVisible();
+
+		if (VISUAL) {
+			await expect(page).toHaveScreenshot('stammbaum-bottom-sheet-414.png', {
+				animations: 'disabled'
+			});
+		}
+
+		// Dismiss via the backdrop and confirm the sheet closes (state survives).
+		await page.getByRole('button', { name: 'Schließen' }).first().click();
+		await expect(sheet).toBeHidden();
+	});
+});