Map Leader in the Python host model; record acadrust W blockers

Adds Leader validation and annotation/dimension-style reference checks to
ocs_plugin_api, maps 15 writable and 5 read-only fields in the adapter, and
adds staged_python_leader_lifecycle_over_real_ipc covering C/R/E/D/U/I/V/P.
The W gate stays open: acadrust's DXF writer omits the annotation handle and
DXF reads drop annotation_offset; DWG R2010+ does not store text size or the
hookline flag. Each gap is pinned by a canary assertion.

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

crates/ocs_plugin_api/build.rs

@@ -756,6 +756,23 @@ fn generate_entity_coverage(out_dir: &Path, registry: &TypeRegistry) {
                             | "paths"
                             | "seed_points"
                     )
+                    | (
+                        "Leader",
+                        "dimension_style"
+                            | "arrow_enabled"
+                            | "path_type"
+                            | "creation_type"
+                            | "hookline_direction"
+                            | "hookline_enabled"
+                            | "text_height"
+                            | "text_width"
+                            | "vertices"
+                            | "annotation_handle"
+                            | "normal"
+                            | "horizontal_direction"
+                            | "block_offset"
+                            | "annotation_offset"
+                    )
             ) {
                     "transaction_geometry"
             } else {