# Contour Service

## Description
Service for detecting and scoring wire/line contours from Vision results.

## Acceptance Criteria
- [ ] `ContourService` class with methods:
  - `func findBestWireContour(at point: CGPoint, from contours: [VNContour]) -> VNContour?`
  - `func scoreContour(_ contour: VNContour, relativeTo point: CGPoint) -> Float`
  - `func contourToMask(_ contour: VNContour, width: Int, imageSize: CGSize) -> CGImage`
- [ ] Contour scoring considers:
  - Proximity to tap point (closer = higher score)
  - Aspect ratio (thin and elongated = higher score)
  - Straightness / low curvature (straighter = higher score)
  - Length (longer = higher score)
- [ ] Configurable mask width: default 6px, range 2-20px
- [ ] Returns `nil` when no wire-like contour found near tap
- [ ] Unit tests for contour scoring logic

## Technical Notes
- VNContour provides normalized path points
- Calculate curvature by analyzing angle changes along path
- Aspect ratio = length / average width
- Weight scoring factors: proximity (0.3), aspect (0.3), straightness (0.2), length (0.2)

## Edge Cases
- No contours detected: return nil
- All contours score below threshold: return nil
- Curved wires: allow moderate curvature, don't require perfectly straight
- Contour very close to tap but not wire-like: score should be low