ocs_doc_api: Phase 2b-b (Hatch)

- CreateHatch(HatchSpec) op + GetHatchBoundary query (append-only).
- HatchSpec{boundary: Vec<[f64;2]>, solid}; executor validates >= 3 boundary points.
- backend add_hatch (Line-edge BoundaryPath, solid/pattern) + hatch_boundary
  (reconstruct loops from Line edges; non-line edges -> Unsupported).
- Hatch bounds from boundary edges; facade create_hatch + Entity handle.
- spec Hatch family; api_reference + binding_schema regenerated; mocks + baseline.
- Test phase2b_hatch_create_boundary_bounds_delete -> 606 host lib + 8 crate + 3 consistency green.

crates/ocs_doc_api/src/gen/binding_schema.json

@@ -258,6 +258,25 @@
       ],
       "name": "MText"
     },
+    {
+      "acadrust_variant": "Hatch",
+      "collection": "curves",
+      "handle": "Entity",
+      "methods": [
+        {
+          "args": [],
+          "bulk": false,
+          "fixed": null,
+          "kind": "query",
+          "name": "boundary",
+          "op": null,
+          "query": "GetHatchBoundary",
+          "read_only": true,
+          "returns": "Vec<Vec<[f64; 2]>>"
+        }
+      ],
+      "name": "Hatch"
+    },
     {
       "acadrust_variant": "Insert",
       "collection": "entities",