Audit AttributeDefinition through both formats; pin the DXF reader gap

Compares every writable ATTDEF field through DWG and DXF. DWG round-trips the
complete state; acadrust's DXF reader handles only eight group codes, so
alignment, width factor, oblique angle, attribute flags, field length,
generation flags, lock and text style reopen as defaults. Pinned by canary
expectations and recorded in the ledger.

Co-Authored-By: Claude Sonnet 5 <[email protected]>

docs/plugin-host-model-completion-plan.md

@@ -172,3 +172,4 @@ exact queue above and update statuses with evidence after each increment.
 - Recorded `SectionSymbol` (queue item 15) as **blocked**: it needs a section view style and view representation the host cannot create, and its raw point-count fields have no documented derivation. Mapped `Light` (item 16); every gate passes except DXF `cast_shadows`, which the reader drops (pinned by a canary). The queue now continues with `Region`.
 - Recorded `Region`, `Body`, `Solid3D`, `Surface` (queue items 17-20) and `Ole2Frame` (item 21) as **blocked**. The ACIS kinds need a host-side kernel-backed create/transform API that regenerates the payload, wires and silhouettes; the OLE frame needs a valid embedded-storage fixture. No opaque payload is rewritten. With this the ordered queue is complete: 12 kinds are fully complete, Leader, Helix, Underlay, ViewBorder and Light are mapped but blocked at DWG/DXF persistence by acadrust gaps, RasterImage and Viewport lack an oracle or linkage, and six kinds are blocked. Next work is the engine fixes behind the canary assertions, the mapped-kind audit of the 17 pre-existing kinds, and merging `origin/main`.
 - Audited the 17 pre-existing mapped kinds through the shared real-runner driver (`audit_python_*`). The audit found and fixed genuine validation gaps: Ellipse had none, Text and MText accepted a zero height, Arc accepted non-finite angles, Point and Line accepted infinite thickness, and most basic kinds had no creation-time validation. A shared `validate_basic_entity` now covers Point, Line, Circle, Arc, Ellipse, Text, MText, LwPolyline, Polyline, Polyline2D, Polyline3D and Spline, refusing only problems an edit introduces so already-invalid legacy values stay editable. Twelve of the 17 kinds now pass every gate (Point, Line, Circle, Arc, Ellipse, LwPolyline, Text, MText, Ray, XLine, Solid, Face3D). Four expose persistence findings pinned by canaries (Polyline reopens as Polyline3D; Polyline2D reopens as LwPolyline in DXF; Polyline3D loses elevation in DWG; Spline loses weights in DXF), and Insert is update-only with all applicable gates passing. The driver gained per-format DWG expectations and a host-made block fixture for Insert.
+- Audited `AttributeDefinition` against acadrust `5b682ed` with a full-field comparison through both formats. Everything passes in DWG. DXF keeps only tag, prompt, value, insertion point, height and rotation because the reader handles eight group codes; alignment, width factor, oblique angle, attribute flags, field length, generation flags, lock and text style reopen as defaults. The kind stays integration-tested and the gap is pinned by canary expectations; the fix belongs in cadcodec's `read_attdef`. The shared driver's block fixture now also serves `MAKEBLOCK` scripts.