[AZ-455] Decompose Step 3 — test task specs (AZ-457..AZ-482)

Adds 26 blackbox-test task specs under epic AZ-455 plus the matching
rows in _dependencies_table.md. Each task depends on AZ-456 (test
infrastructure). Advances autodev existing-code flow Step 5 → Step 6
(Implement Tests, cycle 1) ready for batch implementation.

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

_docs/02_tasks/todo/AZ-462_test_overlay_membership.md

@@ -0,0 +1,57 @@
+# Test — Annotation Overlay Window Membership
+
+**Task**: AZ-462_test_overlay_membership
+**Name**: Overlay membership at the in-window edges
+**Description**: Pin the 4 inclusive/exclusive edge cases for the annotation overlay window (FT-P-14, FT-P-15, FT-N-01, FT-N-02). These edges have caused subtle off-by-one regressions before; without explicit edge-tests they recur silently.
+**Complexity**: 2 points
+**Dependencies**: AZ-456_test_infrastructure
+**Component**: 06_annotations (overlay window) (Blackbox Tests)
+**Tracker**: AZ-462
+**Epic**: AZ-455
+
+## Problem
+
+The overlay window logic asserts an annotation is "in-window" iff `lowerBound <= ts <= upperBound`. Off-by-one mistakes (strict instead of inclusive, or shifted by one frame interval) only surface when the playback head is exactly on the boundary — a state that test scenarios rarely hit by accident.
+
+## Outcome
+
+- 4 edge-case scenarios pass per the inclusive-boundary contract.
+- Tests are deterministic — they construct exact-edge fixtures rather than relying on real-time playback.
+
+## Scope
+
+### Included
+
+| Scenario | Profile | Source file |
+|----------|---------|-------------|
+| FT-P-14 — overlay membership at the lower in-window edge | fast | blackbox-tests.md |
+| FT-P-15 — overlay membership at the upper in-window edge | fast | blackbox-tests.md |
+| FT-N-01 — overlay annotation below the lower bound is NOT rendered | fast | blackbox-tests.md |
+| FT-N-02 — overlay annotation above the upper bound is NOT rendered | fast | blackbox-tests.md |
+
+### Excluded
+
+- Overlay style / Z-order / color (covered by class-color tests in component scenarios).
+- Overlay clicking / selection (covered by 16_test_canvas_bbox).
+
+## Acceptance Criteria
+
+**AC-1: Inclusive boundary**
+FT-P-14 / FT-P-15 assert an annotation EXACTLY on `lowerBound` (resp. `upperBound`) IS rendered in the overlay.
+
+**AC-2: Strict exclusion**
+FT-N-01 / FT-N-02 assert an annotation one frame interval before / after the window is NOT rendered.
+
+**AC-3: Reads the DOM, not internal state**
+The "rendered" assertion queries the canvas / overlay DOM nodes (or rendered SVG / Leaflet markers). It does NOT inspect React component state.
+
+## System Under Test Boundary
+
+- System under test: `<CanvasEditor>` + overlay annotation rendering.
+- Allowed stubs: MSW for annotation list responses (the fixture pins exact timestamps).
+- Disallowed: stubbing the overlay logic itself, or asserting on React state.
+- Expected observables compared against `results_report.md` rows for FT-P-14, 15, FT-N-01, 02.
+
+## Constraints
+
+- Fixtures must pin timestamps to exact boundaries via deterministic numeric values; no `new Date()` or similar.