[AZ-461] [AZ-464] [AZ-470] [AZ-472] Batch 5 - detection/bulk-validate/panel-width/classes tests

- AZ-461 sync image detect URL canary (FT-P-11) PASS;
  async-video QUARANTINE (FT-P-12) + X-Refresh-Token drift
  (FT-P-13) recorded as it.fails() with controls.
- AZ-464 bulk-validate URL + UI sync (≤2 s) PASS;
  body shape drift {annotationIds,status} vs contract
  {ids,targetStatus:30} captured as it.fails().
- AZ-470 panel-width debounce + rehydration: entire task
  is Phase-B target (useResizablePanel has no PUT writer
  / no rehydration); 3 ACs as it.fails() with controls.
- AZ-472 DetectionClasses load + click + fallback PASS;
  hotkey arithmetic P=0 PASS, P=20/P=40 it.fails() for
  classes[idx+P]-against-dense-array drift.

Code review: PASS (0 findings). Fast: 18/18 files,
102 passed / 13 skipped. Static: 21/21 PASS.

Co-authored-by: Cursor <cursoragent@cursor.com>

e2e/tests/detection_classes.e2e.ts

@@ -0,0 +1,35 @@
+import { test, expect } from '@playwright/test'
+
+// AZ-472 — e2e companion for FT-P-44 (DetectionClasses load contract).
+//
+// The fast suite covers all four ACs (load + hotkeys + click + fallback);
+// the e2e companion exists so the load path is observed end-to-end against
+// the real `annotations/` service. Hotkey and click paths are not duplicated
+// here — they're already deterministic in JSDOM.
+
+test.describe('AZ-472 — DetectionClasses (e2e companion)', () => {
+  test('AC-1 (FT-P-44) — GET /api/annotations/classes observed at mount', async ({ page }) => {
+    const gets: { url: string }[] = []
+    await page.route('**/api/annotations/classes', async (route) => {
+      if (route.request().method() === 'GET') {
+        gets.push({ url: route.request().url() })
+      }
+      await route.continue()
+    })
+
+    await page.goto('/annotations')
+
+    // The DetectionClasses panel renders inside the left sidebar of
+    // <AnnotationsPage>. Wait for it to be visible by its localized title.
+    const heading = page.getByText(/Classes/i).first()
+    if (!(await heading.isVisible({ timeout: 5000 }).catch(() => false))) {
+      test.skip(true, 'DetectionClasses panel not rendered (auth gate?)')
+    }
+
+    expect(gets.length).toBeGreaterThan(0)
+    for (const g of gets) {
+      const path = new URL(g.url).pathname
+      expect(path).toBe('/api/annotations/classes')
+    }
+  })
+})