Refactor task management structure and update documentation

- Changed the directory structure for task specifications to include a dedicated `todo/` folder within `_docs/02_tasks/` for tasks ready for implementation.
- Updated references in various skills and documentation to reflect the new task lifecycle, including changes in the `implementer` and `decompose` skills.
- Enhanced the README and flow documentation to clarify the new task organization and its implications for the implementation process.

These updates improve task management clarity and streamline the implementation workflow.

_docs/02_tasks/done/AZ-162_test_nms.md

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+# NMS Overlap Removal Tests
+
+**Task**: AZ-162_test_nms
+**Name**: NMS Overlap Removal Tests
+**Description**: Implement 3 tests for non-maximum suppression — overlapping kept by confidence, non-overlapping preserved, chain overlap resolution
+**Complexity**: 1 point
+**Dependencies**: AZ-152_test_infrastructure
+**Component**: Blackbox Tests
+**Jira**: AZ-162
+**Epic**: AZ-151
+
+## Problem
+
+The NMS module removes overlapping detections based on IoU threshold (0.3), keeping the higher-confidence detection. Tests verify all overlap scenarios.
+
+## Outcome
+
+- 3 passing pytest tests in `tests/test_nms.py`
+
+## Scope
+
+### Included
+- BT-NMS-01: Overlapping detections — keep higher confidence (IoU > 0.3 → 1 kept)
+- BT-NMS-02: Non-overlapping detections — keep both (IoU < 0.3 → 2 kept)
+- BT-NMS-03: Chain overlap resolution (A↔B, B↔C → ≤ 2 kept)
+
+### Excluded
+- Integration with inference pipeline (separate task)
+
+## Acceptance Criteria
+
+**AC-1: Overlap removal**
+Given 2 Detections at same position, confidence 0.9 and 0.5, IoU > 0.3
+When remove_overlapping_detections() runs
+Then 1 detection returned (confidence 0.9)
+
+**AC-2: Non-overlapping preserved**
+Given 2 Detections at distant positions, IoU < 0.3
+When remove_overlapping_detections() runs
+Then 2 detections returned
+
+**AC-3: Chain overlap**
+Given 3 Detections: A overlaps B, B overlaps C, A doesn't overlap C
+When remove_overlapping_detections() runs
+Then ≤ 2 detections; highest confidence per overlapping pair kept
+
+## Constraints
+
+- Detection objects constructed in-memory (no fixture files)
+- IoU threshold is 0.3 (from constants or hardcoded in NMS)