The latter is intended for a specific solver constraint.
[Sketcher] Make further changes for tangent-at-knot separation
1. Remove code for tangent-at-knot from `addAngleAtPointConstraint`.
2. Use correct order of input.
3. Separate internal C0 knot vs end knots. The latter can still be constrained
but the user must use endpoints of the spline instead of knots.
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