Map ViewBorder in the Python host model; record DXF kind blocker

Bounds, scale and rotation are writable with viewport and scale reference
rules. staged_python_view_border_lifecycle_over_real_ipc passes every gate
in DWG; a DXF DRAWINGVIEW reopens as an opaque entity, pinned by a canary.

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

plugins/opencad-python/README.md

@@ -94,7 +94,7 @@ The host-owned catalog classifies all 48 entity variants and tracks every
 traced field, including fields marked `unmapped`. Query it with
 `doc.coverage()` or `doc.coverage("Line")`; each row includes source field,
 type, access, and current validation status. Geometry edits remain limited to
-the 35 mapped kinds.
+the 36 mapped kinds.
 For any entity, `entity.snapshot` returns a detached dictionary of its raw
 CAD fields, including `snapshot["common"]` and kind-specific nested values.
 It can inspect an unmapped kind; editing the dictionary does

plugins/opencad-python/entity_manifest.json

@@ -34,7 +34,8 @@
     "RasterImage",
     "Wipeout",
     "Underlay",
-    "Viewport"
+    "Viewport",
+    "ViewBorder"
   ],
   "manual_kinds": ["Dimension"],
   "base_fields": ["handle", "layer", "owner_handle"],
@@ -403,6 +404,15 @@
         "width": { "required": true },
         "height": { "required": true }
       }
+    },
+    "ViewBorder": {
+      "fields": {
+        "version": { "read_only": true },
+        "min": { "required": true },
+        "max": { "required": true },
+        "active_viewport": { "required": true },
+        "scale_handle": { "required": true }
+      }
     }
   }
 }

plugins/opencad-python/src/ocs_module.rs

@@ -4756,7 +4756,7 @@ mod tests {
                 );
             }
         }
-        assert_eq!(emitted.len(), 35);
+        assert_eq!(emitted.len(), 36);
     }
 
     #[cfg(feature = "experimental-host-model")]