Vectors, GEO and MEMBER records, member placement, sleeve and cavity
paths, exact polyline distance, corner-radius derivation, and the
monotone solver. Direct translation of legacy/openscad/lib/sb-geom.scad
at rev 8.0.0.
Angles stay in degrees, matching OpenSCAD, so every expression reads the
same as its source line. The 44 solver iterations, the 0.999 and 0.98
scale factors, the 0.05/179.95 cutoffs and the 1e9 sentinel are
reproduced exactly: they shaped the frozen oracle.
Region operations are not included -- they need a 2D boolean kernel and
follow with the Shapely layer.
49 unit tests, none of which touch the oracle. Harness proven by
mutation: radians for degrees, a shortened solver, a dropped scale
factor, a skipped crossing test and a flipped offset sign are each
caught. Oracle acceptance still skips; 236 unchanged.
