Fix MOT tracking label clipping at image boundaries

[Copilot]

MOT tracking labels (TID/CID) positioned at y1 - vertical_offset become invisible when bounding boxes appear near the image top, as the calculated y-coordinate goes negative or clips at the edge.

Changes

• Label positioning logic (basenode.py, draw_util.py)

  • Add 5px margin check before positioning labels above bbox
  • Reposition labels inside bbox when y_pos < margin
  • Preserve TID/CID ordering and spacing in both positions

• Test coverage (test_mot_label_visibility.py)

  • Validate positioning logic across edge cases (y=0, small y1, sufficient space)
  • Verify implementation in both draw functions

# Before: Always above bbox (clips at top)
cv2.putText(image, text, (x1, y1 - vertical_offset_1), ...)

# After: Reposition when too close to edge
tid_y_pos = y1 - vertical_offset_1
if tid_y_pos < 5:
    tid_y_pos = y1 + vertical_offset_1  # Inside bbox
cv2.putText(image, text, (x1, tid_y_pos), ...)

Normal positioning (labels above bbox) remains unchanged when sufficient space exists.

Original prompt

le tracking est non visible sur MOT, verifie est fix

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