The codec now holds wide EntityType variants boxed (MText, Helix,
Dimension, Hatch, Viewport, MultiLeader, Surface, Table, Ole2Frame,
Light, Extended). Constructors box their entity; nested patterns reach
a dimension through entities::dimension::as_dimension(_mut). Also
follows BlockAction::action_ids, LineTypeComplexData::source_flags and
the decimal tab stop with an explicit character.
Co-Authored-By: Claude Opus 5.5 <noreply@anthropic.com>
Expose creation fields, constraints and examples for the 11 supported types without expanding startup tool schemas. Share the creation contract and constructor with execution to keep accepted inputs consistent.
Validation: MCP, contract/factory and entity creation regression tests.
