Extend wedgeGeometry to make gambrel and round roofs

Instead of specifying where the "center point" is, specify the angle (or max height) and number of crossing lines. if one, cross in the middle, allow user to specify a function for the height.

Start by locating the wedgeGeometry entry point and reading how the current center point is specified; the issue names no files or tests. Clarify the API and expected geometry for gambrel and round roofs, including angle or maximum height, crossing-line count, midpoint behavior, and a user-supplied height function. Done means those cases are implemented with clear tests or examples.

Written by the indexing model from the issue text.