Use @property/@setter for writable mathutils properties

Writable mathutils properties (Vector, Euler, etc.) were typed as plain
attributes with a union type, causing the getter to also return the union.
This made `obj.location.x` fail type checking since Sequence[float] has
no `.x`. Now these properties use @property for the getter (returning the
concrete mathutils type) and @setter accepting the wider union.

Co-Authored-By: Claude Opus 4.6 (1M context) <noreply@anthropic.com>

introspect.py

@@ -194,7 +194,11 @@ class VariableData(TypedDict):
     value: str
 
 
-class PropertyData(TypedDict):
+class _PropertyDataOptional(TypedDict, total=False):
+    setter_type: str
+
+
+class PropertyData(_PropertyDataOptional):
     name: str
     type: str
     is_readonly: bool
@@ -1552,14 +1556,15 @@ def _property_data_from_member(
     else:
         is_readonly = not _is_getset_writable(cls, name)
     prop_type = rtype or "object"
-    if not is_readonly and prop_type in _MATHUTILS_ARRAY_TYPES:
-        prop_type = f"{prop_type} | Sequence[float]"
-    return {
+    result: PropertyData = {
         "name": name,
         "type": prop_type,
         "is_readonly": is_readonly,
         "description": doc,
     }
+    if not is_readonly and prop_type in _MATHUTILS_ARRAY_TYPES:
+        result["setter_type"] = f"{prop_type} | Sequence[float]"
+    return result
 
 
 def _introspect_declared_class_members(
@@ -2661,17 +2666,16 @@ def _rna_struct_to_data(
     for prop in getattr(struct_info, "properties", []):
         prop_type = rna_property_to_type(prop)
         is_readonly = bool(getattr(prop, "is_readonly", False))
+        prop_data: PropertyData = {
+            "name": str(getattr(prop, "identifier", "")),
+            "type": prop_type,
+            "is_readonly": is_readonly,
+            "description": str(getattr(prop, "description", "") or ""),
+        }
         # Writable mathutils properties also accept Sequence[float] for assignment
         if not is_readonly and prop_type in _MATHUTILS_ARRAY_TYPES:
-            prop_type = f"{prop_type} | Sequence[float]"
-        properties.append(
-            {
-                "name": str(getattr(prop, "identifier", "")),
-                "type": prop_type,
-                "is_readonly": is_readonly,
-                "description": str(getattr(prop, "description", "") or ""),
-            }
-        )
+            prop_data["setter_type"] = f"{prop_type} | Sequence[float]"
+        properties.append(prop_data)
 
     methods: list[FunctionData] = []
     is_collection_wrapper = sid in collection_element_types