test: add e2e suite for core comparison flows

Adds 17 new specs across six files plus the supporting POM
infrastructure:

- fixtures with auto-opened comparison + typography helpers
- TypographyMenu POM reading values from ComboControl aria-labels
- ComparisonPage extended with side selection, font picking,
  slider-value reader, FontFaceSet inspection, storage snapshot
- compare-flow: A/B selection, aria-pressed state, storage write
- preview-text: input binding + slider character rendering
- slider: keyboard ARIA contract (Arrow / Shift+Arrow / Page / Home / End)
- font-loading: FontFaceSet contains selected, excludes unrelated
- persistence: font selection + typography settings survive reload
- typography: symmetric increase/decrease for all four controls

e2e/persistence.test.ts

@@ -0,0 +1,41 @@
+import {
+    expect,
+    test,
+} from './fixtures';
+
+test.describe('persistence', () => {
+    test('restores selected fonts after reload', async ({ comparison, page }) => {
+        await comparison.pickPair('Inter', 'Roboto');
+
+        // Confirm the store has flushed before reloading — otherwise we race
+        // the debounce and may reload with empty storage.
+        await expect.poll(async () => {
+            const storage = await comparison.readStorage();
+            return storage['glyphdiff:comparison'];
+        }).toMatch(/roboto/i);
+
+        await page.reload();
+        await comparison.searchInput.waitFor({ state: 'visible' });
+
+        await expect(comparison.primaryFont).toContainText('Inter');
+        await expect(comparison.secondaryFont).toContainText('Roboto');
+    });
+
+    test('restores typography settings after reload', async ({ comparison, typography, page }) => {
+        const baseline = await typography.readValue('size');
+        await typography.bump('size', 'up', 2);
+
+        const bumped = await typography.readValue('size');
+        expect(bumped).not.toBe(baseline);
+
+        await expect.poll(async () => {
+            const storage = await comparison.readStorage();
+            return storage['glyphdiff:comparison:typography'];
+        }).not.toBeNull();
+
+        await page.reload();
+        await comparison.searchInput.waitFor({ state: 'visible' });
+
+        expect(await typography.readValue('size')).toBe(bumped);
+    });
+});