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>

generate_stubs.py

@@ -89,6 +89,9 @@ def collect_all_type_strings(module_data: ModuleData) -> list[str]:
             all_types.append(base)
         for prop in struct["properties"]:
             all_types.append(prop["type"])
+            setter_type = prop.get("setter_type")
+            if setter_type:
+                all_types.append(setter_type)
         for method in struct["methods"]:
             for param in method["params"]:
                 if param["type"]:
@@ -367,7 +370,9 @@ def generate_property_stub(
     property_decorator: str = "@property",
 ) -> str:
     """Generate a stub for a class property."""
-    if prop["is_readonly"]:
+    setter_type = prop.get("setter_type")
+
+    if prop["is_readonly"] or setter_type:
         result = f"{indent}{property_decorator}\n"
         result += f"{indent}def {prop['name']}(self) -> {prop['type']}:\n"
         if prop["description"]:
@@ -377,6 +382,11 @@ def generate_property_stub(
             result += f'{indent}    """{desc}"""\n'
         else:
             result += f"{indent}    ...\n"
+        if setter_type:
+            result += f"\n{indent}@{prop['name']}.setter\n"
+            result += (
+                f"{indent}def {prop['name']}(self, value: {setter_type}) -> None: ...\n"
+            )
         return result
 
     result = f"{indent}{prop['name']}: {prop['type']}\n"
@@ -413,6 +423,7 @@ def fixup_shadowed_builtins(
     fixed: list[PropertyData] = []
     for prop in properties:
         new_type = prop["type"]
+        new_setter_type = prop.get("setter_type")
         for name in shadowed:
             # Replace bare builtin type references with builtins.X
             # e.g. "int" -> "builtins.int", "list[int]" -> "list[builtins.int]"
@@ -421,14 +432,21 @@ def fixup_shadowed_builtins(
                 f"builtins.{name}",
                 new_type,
             )
-        fixed.append(
-            {
-                "name": prop["name"],
-                "type": new_type,
-                "is_readonly": prop["is_readonly"],
-                "description": prop["description"],
-            }
-        )
+            if new_setter_type:
+                new_setter_type = re.sub(
+                    rf"\b{name}\b",
+                    f"builtins.{name}",
+                    new_setter_type,
+                )
+        new_prop: PropertyData = {
+            "name": prop["name"],
+            "type": new_type,
+            "is_readonly": prop["is_readonly"],
+            "description": prop["description"],
+        }
+        if new_setter_type:
+            new_prop["setter_type"] = new_setter_type
+        fixed.append(new_prop)
     return fixed