CAD-like constraint-based modeling

Coming from the world of CAD I would really like it if constraints were available for modelling. They can be really useful when changing a design but wanting some features to be connected a certain way. The alternative way of doing this without constraints would be to scale every component independently and moving them around until thing look right.

I haven't seen in into any other program (other than point coincident contraint) and I think it would be really useful.

The issue names no files, tests, or entry points. Start by surveying the modeling architecture and existing point-coincident constraint support, then clarify which constraint types and design behavior are in scope before implementation; done should be defined by agreed constraint behavior and coverage.

Written by the indexing model from the issue text.