Fix ConvexHull to return points in counter-clockwise order (#6810)

* Fix ConvexHull to return points in counter-clockwise order

- Add sortCounterClockwise method to ensure CCW ordering
- Start from bottom-most, left-most point for deterministic results
- Fix issue where unordered HashSet broke downstream algorithms
- Add comprehensive tests with CCW order verification

* test(geometry): Achieve 100% test coverage for ConvexHull