Complete MLine host model coverage

Maps vertices, flags, justification, normal, scale and style with host
validation and MLineStyle binding. The host recomputes vertex direction,
miter and element parameters on scripted create/edit, so scripts only supply
positions. staged_python_mline_lifecycle_over_real_ipc passes the full gate
including DWG and DXF reopen.

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

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

@@ -7,13 +7,13 @@ Build a general Python document model over the OCS host API for all **43 canvas
 As of 20 September 2026, the working branch is `plugin/host-model-api` at
 `a8dd3640` plus the Leader increment, published as draft PR
 [#1391](https://github.com/HakanSeven12/OpenCADStudio/pull/1391). Host API is
-v7. The Python feature has explicit writes for **23 of 43** canvas kinds: 22
-are creatable and `Insert` remains update-only. This is **not** 23 completed
-kinds: Tolerance, Shape, AttributeEntity and Hatch pass every completion gate.
+v7. The Python feature has explicit writes for **24 of 43** canvas kinds: 23
+are creatable and `Insert` remains update-only. This is **not** 24 completed
+kinds: Tolerance, Shape, AttributeEntity, Hatch and MLine pass every completion gate.
 AttributeDefinition passes its host and real IPC lifecycle but remains short of
 `Complete` because the previously pinned CAD codec dropped optional ATTDEF
 fields during DXF reads; revalidate that blocker against the current
-`acadrust` revision `7ea4247`. Leader is mapped and integration-tested but blocked at W by three acadrust persistence gaps (see the ledger). The other 20 canvas kinds have only `layer`
+`acadrust` revision `7ea4247`. Leader is mapped and integration-tested but blocked at W by three acadrust persistence gaps (see the ledger). The other 19 canvas kinds have only `layer`
 writes through the document model. All 43 have raw typed snapshots. There are
 three internal records and two opaque fallbacks outside the 43 canvas kinds.
 
@@ -123,7 +123,7 @@ The last five may require new engine capabilities rather than only Python conver
 
 ## Handoff start point
 
-Continue with **MLine** (queue item 2). Leader is done except for its W
+Continue with **Dimension** (queue item 3; track each subtype separately). Leader is done except for its W
 gate; when the engine writes DXF group 340, reads group 213 and the DWG
 R2010+ text-size question is decided, flip the canary assertions in
 `staged_python_leader_lifecycle_over_real_ipc` and mark it `Complete`.
@@ -158,3 +158,4 @@ exact queue above and update statuses with evidence after each increment.
 - Completed `Hatch` with full solid/pattern definitions and typed nested boundary paths. The adapter generator now handles single-payload tagged enums as `{kind, value}` dictionaries, which covers every Hatch edge variant and is reusable by later nested entity models. Unknown adapter properties are rejected instead of being silently ignored.
 - `staged_python_hatch_lifecycle_over_real_ipc` passes C/R/E/D/U/I/W/V/P with closed line-loop fixtures: solid creation, conversion to a stored-line pattern, boundary replacement, selection and live render-cache checks, atomic invalid scale/association/open-loop/unmapped-payload rejection, edited/deleted DWG and DXF reopen, post-reopen edits, and three-step undo/redo. Hatch is **Complete**; the queue now continues with `Leader`.
 - Mapped `Leader` (host validation and reference binding in `entity_coverage.rs`, policy/build.rs/manifest entries, adapter count 23). `staged_python_leader_lifecycle_over_real_ipc` passes C/R/E/D/U/I/V/P through the real runner. W is blocked by acadrust: the DXF writer omits the annotation handle (340), DXF reads lose `annotation_offset` (213), and DWG R2010+ does not store text size or hookline flag. Each gap is pinned by a canary assertion so it fails loudly once fixed. The queue now continues with `MLine`.
+- Completed `MLine`. Host validation and style binding live in `ocs_plugin_api`; derived vertex geometry and element parameters are recomputed by the host (`normalize_scripted_mline`) on scripted create/edit, so scripts supply positions only. The adapter maps `flags` as an integer through a manifest override because the generator cannot classify acadrust's serde-newtype `MLineFlags`. `staged_python_mline_lifecycle_over_real_ipc` passes C/R/E/D/U/I/W/V/P with DWG and DXF reopen. The queue now continues with `Dimension`.