[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>

_docs/02_tasks/done/AZ-472_test_detection_classes.md

@@ -0,0 +1,59 @@
+# Test — DetectionClasses (Load, Hotkeys, Click, Fallback)
+
+**Task**: AZ-472_test_detection_classes
+**Name**: DetectionClasses load + 1-9 hotkeys + click path + empty/5xx fallback
+**Description**: Implement the 4 blackbox tests pinning `<DetectionClasses>` behavior: load from `/api/annotations/classes`, hotkey 1-9 → `classes[(key-1) + P]` (P = current PhotoMode offset), click-to-select path, and the fallback list when the API is empty or 5xx.
+**Complexity**: 3 points
+**Dependencies**: AZ-456_test_infrastructure
+**Component**: 06_annotations (DetectionClasses) + 11_class-colors (Blackbox Tests)
+**Tracker**: AZ-472
+**Epic**: AZ-455
+
+## Problem
+
+`<DetectionClasses>` is keyboard-driven during annotation; the hotkey-to-class mapping changes with PhotoMode (offset P). Wrong P leaks the wrong class number on save — a quality regression hard to spot without explicit hotkey tests.
+
+## Outcome
+
+- 4 scenarios pass — load contract, hotkey arithmetic, click selection, fallback robustness.
+
+## Scope
+
+### Included
+
+| Scenario | Profile | Source file |
+|----------|---------|-------------|
+| FT-P-44 — DetectionClasses loads from `/api/annotations/classes` | fast + e2e | blackbox-tests.md |
+| FT-P-45 — class hotkey 1–9 selects `classes[(key-1) + P]` | fast | blackbox-tests.md |
+| FT-P-46 — class click path | fast | blackbox-tests.md |
+| FT-P-47 — fallback class list on API empty/5xx | fast | blackbox-tests.md |
+
+### Excluded
+
+- PhotoMode switching itself (covered in 18_test_photo_mode).
+- Class CRUD via Admin (out of scope; per-feature task in Phase B).
+
+## Acceptance Criteria
+
+**AC-1: Load contract**
+FT-P-44 — outbound URL is `/api/annotations/classes`; response shape matches `seed_classes` (per the contract).
+
+**AC-2: Hotkey arithmetic**
+FT-P-45 — for each PhotoMode P ∈ {0, 20, 40}, pressing keys 1..9 selects the corresponding class from the appropriate window of 9.
+
+**AC-3: Click**
+FT-P-46 — clicking a class entry selects that class; outbound annotation save (if any) carries the right classId.
+
+**AC-4: Fallback**
+FT-P-47 — when `/api/annotations/classes` returns 200 with `[]` or any 5xx, the fallback class list is rendered; tests assert the fallback length and a marker indicating fallback mode.
+
+## System Under Test Boundary
+
+- System under test: `<DetectionClasses>` + `<PhotoModeContext>` (read-only here).
+- Allowed stubs: MSW for `/api/annotations/classes`.
+- Disallowed: stubbing `<DetectionClasses>` or reading its React state.
+- Expected observables per `results_report.md` rows 73-77 (Group 16).
+
+## Constraints
+
+- `seed_classes` MUST satisfy N≥9 (per test-data.md) so all hotkeys 1..9 are hot in P=0.