Model and Shape

The former combined reference is now split so lifecycle, geometry, and exchange contracts can be documented precisely.

• Model: session lifecycle, construction groups, workplanes, and dynamic dispatch.
• Shape: ownership, measurements, validation, surface evidence, mesh, preview, and export.
• Sessions, handles, and frames: low-level ownership and coordinate context.
• Creation and import, features and transforms, and topology/query/exchange: operation-level guidance.
• Generated symbols: Model and Shape.