Fix Inventor adapter for live Inventor 2025 COM API

The adapter and tests were written against assumed API signatures that
didn't match Inventor 2025.2's actual COM interface. All 54 round-trip
tests now pass against a live Inventor instance.

Key fixes: document type constant (12290 not 12163), ellipse/arc APIs
use UnitVector2d and scalar radii, dimension methods renamed (AddRadius
not AddRadiusDimension), AddTwoPointDistance requires orientation enum,
coincident uses SketchPoint.Merge not AddCoincident, vertex_map uses
duck-typing instead of type().__name__ (always 'CDispatch' via late
binding), point filtering uses _oleobj_ equality for COM identity.

Co-Authored-By: Claude Opus 4.6 (1M context) <noreply@anthropic.com>

Author: CodeReclaimers