Improve assignment reliability by making leader-line tracing the primary signal in dense drawings.
Acceptance criteria:
- Trace from bubble boundary toward line segments, arrowheads, and nearest callout text.
- Penalize assignments that jump across unrelated table/grid geometry.
- Add visual debug overlays for traced path, endpoint, and selected callout.
- Add regression cases for dense drawings with nearby unrelated dimensions.
Improve assignment reliability by making leader-line tracing the primary signal in dense drawings.
Acceptance criteria: