Draft cadcodec issues for the DXF reader gaps; fix Spline rational flag

Documents six cadcodec reader/writer gaps with source references, canary
tests and suggested fixes (nothing filed). Verifying them showed the Spline
DXF weight loss was an OCS bug: the writer emits weights only for a rational
spline, so the host now sets flags.rational from the weights. Spline passes
every gate.

Co-Authored-By: Claude Sonnet 5 <noreply@anthropic.com>

docs/plugin-host-model-coverage-ledger.md

@@ -1,6 +1,6 @@
 # OCS canvas kind coverage ledger
 
-Use with [the completion plan](plugin-host-model-completion-plan.md). This ledger is current as of 20 September 2026: **37 of 43 canvas kinds have explicit geometry writes** (36 creatable, plus update-only legacy `Polyline`), **25 kinds are complete**, and 6 remain layer-only (one of them, SectionSymbol, blocked). `Mapped` means at least one non-layer field is exposed for Python writes; it does **not** mean the kind passes the completion gate. `Update-only` means Python creation is unavailable. `Layer-only` means raw inspection and canvas layer edits exist, but geometry is not mapped. Record actual evidence or a blocking issue before changing any status to `Complete`.
+Use with [the completion plan](plugin-host-model-completion-plan.md). This ledger is current as of 20 September 2026: **37 of 43 canvas kinds have explicit geometry writes** (36 creatable, plus update-only legacy `Polyline`), **26 kinds are complete**, and 6 remain layer-only (one of them, SectionSymbol, blocked). `Mapped` means at least one non-layer field is exposed for Python writes; it does **not** mean the kind passes the completion gate. `Update-only` means Python creation is unavailable. `Layer-only` means raw inspection and canvas layer edits exist, but geometry is not mapped. Record actual evidence or a blocking issue before changing any status to `Complete`.
 
 Completion gate codes: **C** = create through Python document model; **R** = read; **E** = edit defining geometry and another property; **D** = delete; **U** = undo/redo and atomic failure; **I** = real IPC plus GUI/canvas pick or observable behavior; **W** = DWG and DXF save/reopen; **V** = invalid-input checks and untouched-field/reference preservation; **P** = build and load the in-tree bundled plugin with a manifest matching the host toolchain and acadrust source. A kind is `Complete` only when **C/R/E/D/U/I/W/V/P** all pass and its property catalog matches implementation. `Blocked` requires a specific dependency or failing fixture.
 
@@ -15,7 +15,7 @@ Completion gate codes: **C** = create through Python document model; **R** = rea
 | Polyline2D | **Integration-tested / kind changes on DXF save** | Exercised: `vertices`, `closed`, `thickness`. Passes every gate in DWG. DXF reopens a 2-D polyline as an `LwPolyline` (vertices, closure and width survive, but the kind changes and `thickness` is not part of that record's digest here); pinned by a canary expectation. `audit_python_polyline2d_lifecycle_over_real_ipc` (shared `run_mesh_lifecycle`, real runner) passes C/R/E/D/U/I/W/V/P: creation, a two-or-more-property transaction edit with the entity's common data, identity and selection preserved, canvas wires, invalid-input rejection with an atomic multi-entity rollback, DWG and DXF reopen with re-edit, and three-step undo/redo. The audit added the shared `validate_basic_entity` (creation must be valid; an edit is refused only for problems it introduces, so already-invalid legacy values stay editable). |
 | Polyline3D | **Integration-tested / blocked at W by the DWG format (elevation)** | Exercised: `vertices`, `elevation`. Passes every gate in DXF; DWG does not store a 3-D polyline's `elevation`, so it reopens as 0 (pinned by a canary). Vertices persist. `audit_python_polyline3d_lifecycle_over_real_ipc` (shared `run_mesh_lifecycle`, real runner) passes C/R/E/D/U/I/W/V/P: creation, a two-or-more-property transaction edit with the entity's common data, identity and selection preserved, canvas wires, invalid-input rejection with an atomic multi-entity rollback, DWG and DXF reopen with re-edit, and three-step undo/redo. The audit added the shared `validate_basic_entity` (creation must be valid; an edit is refused only for problems it introduces, so already-invalid legacy values stay editable). |
 | LwPolyline | **Complete** | Exercised: `vertices` (with a bulge), `is_closed`, `constant_width`. Rejects fewer than 2 vertices, non-finite locations, bulges and widths, a negative constant width and a zero normal. `audit_python_lwpolyline_lifecycle_over_real_ipc` (shared `run_mesh_lifecycle`, real runner) passes C/R/E/D/U/I/W/V/P: creation, a two-or-more-property transaction edit with the entity's common data, identity and selection preserved, canvas wires, invalid-input rejection with an atomic multi-entity rollback, DWG and DXF reopen with re-edit, and three-step undo/redo. The audit added the shared `validate_basic_entity` (creation must be valid; an edit is refused only for problems it introduces, so already-invalid legacy values stay editable). |
-| Spline | **Integration-tested / blocked at W by acadrust (DXF weights)** | Exercised: `control_points`, `weights`. Validation covers degree, control-point count, knot count and order, weights and finite points. Passes every gate in DWG; the DXF reader does not restore `weights` (a rational spline reopens non-rational; pinned by a canary). `audit_python_spline_lifecycle_over_real_ipc` (shared `run_mesh_lifecycle`, real runner) passes C/R/E/D/U/I/W/V/P: creation, a two-or-more-property transaction edit with the entity's common data, identity and selection preserved, canvas wires, invalid-input rejection with an atomic multi-entity rollback, DWG and DXF reopen with re-edit, and three-step undo/redo. The audit added the shared `validate_basic_entity` (creation must be valid; an edit is refused only for problems it introduces, so already-invalid legacy values stay editable). |
+| Spline | **Complete** | Exercised: `control_points`, `weights`. Validation covers degree, control-point count, knot count and order, weights and finite points. The host sets `flags.rational` whenever weights are present, because the DXF writer emits group 41 only for a rational spline; the audit first showed weights vanishing in DXF and traced it to that missing flag (an OCS bug, not a cadcodec one), now fixed. `audit_python_spline_lifecycle_over_real_ipc` (shared `run_mesh_lifecycle`, real runner) passes C/R/E/D/U/I/W/V/P with DWG and DXF reopen, re-edit, atomic rollback and three-step undo/redo. |
 | Text | **Complete** | Exercised: `text`, `rotation`, `height`. Rejects a non-positive height (previously accepted), a non-positive width factor, non-finite placement and angles, and a zero normal. Style and alignment fields are mapped but not individually exercised. `audit_python_text_lifecycle_over_real_ipc` (shared `run_mesh_lifecycle`, real runner) passes C/R/E/D/U/I/W/V/P: creation, a two-or-more-property transaction edit with the entity's common data, identity and selection preserved, canvas wires, invalid-input rejection with an atomic multi-entity rollback, DWG and DXF reopen with re-edit, and three-step undo/redo. The audit added the shared `validate_basic_entity` (creation must be valid; an edit is refused only for problems it introduces, so already-invalid legacy values stay editable). |
 | MText | **Complete** | Exercised: `text`, `rectangle_width`, `rotation`. Rejects a non-positive height (previously accepted), a negative width, non-finite placement, a non-positive line-spacing factor and a zero normal. Attachment, columns and background fields are mapped but not individually exercised. `audit_python_mtext_lifecycle_over_real_ipc` (shared `run_mesh_lifecycle`, real runner) passes C/R/E/D/U/I/W/V/P: creation, a two-or-more-property transaction edit with the entity's common data, identity and selection preserved, canvas wires, invalid-input rejection with an atomic multi-entity rollback, DWG and DXF reopen with re-edit, and three-step undo/redo. The audit added the shared `validate_basic_entity` (creation must be valid; an edit is refused only for problems it introduces, so already-invalid legacy values stay editable). |
 | Ray | **Complete** | Exercised: `base_point`, `direction`. Unit-direction and finite-point validation already existed; the audit added the full DWG and DXF reopen and re-edit gate. `audit_python_ray_lifecycle_over_real_ipc` (shared `run_mesh_lifecycle`, real runner) passes C/R/E/D/U/I/W/V/P: creation, a two-or-more-property transaction edit with the entity's common data, identity and selection preserved, canvas wires, invalid-input rejection with an atomic multi-entity rollback, DWG and DXF reopen with re-edit, and three-step undo/redo. The audit added the shared `validate_basic_entity` (creation must be valid; an edit is refused only for problems it introduces, so already-invalid legacy values stay editable). |