ocs_doc_api: Phase 2b-c (linear Dimension) — Phase 2 complete

- CreateDimensionLinear(DimensionSpec) op + GetDimensionMeasurement query (append-only).
- backend add_dimension_linear (Dimension::Linear via DimensionLinear::new) +
  dimension_measurement (linear/radius/diameter distance).
- Dimension bounds from measured + definition points; Dimension handle + measurement().
- spec Dimension family; api_reference + binding_schema regenerated; mocks + baseline.
- Test phase2c_dimension_linear_create_measurement_bounds -> 607 host lib + 8 crate
  + 3 consistency green. Phase 2 (full 2D + annotations) is now complete.

crates/ocs_doc_api/src/gen/binding_schema.json

@@ -277,6 +277,25 @@
       ],
       "name": "Hatch"
     },
+    {
+      "acadrust_variant": "Dimension",
+      "collection": "curves",
+      "handle": "Dimension",
+      "methods": [
+        {
+          "args": [],
+          "bulk": false,
+          "fixed": null,
+          "kind": "query",
+          "name": "measurement",
+          "op": null,
+          "query": "GetDimensionMeasurement",
+          "read_only": true,
+          "returns": "f64"
+        }
+      ],
+      "name": "Dimension"
+    },
     {
       "acadrust_variant": "Insert",
       "collection": "entities",
@@ -361,7 +380,8 @@
       "Ray",
       "XLine",
       "Text",
-      "MText"
+      "MText",
+      "Dimension"
     ],
     "root": "DocApi"
   },