feat/stubgen: fix pun field typing error

src/capnp_stubgen/gen_struct.py

@@ -60,14 +60,9 @@ def generate_struct(
                 non_union_fields.append((field_name, field_type_str))
 
         elif "group" in field:
-            group_type_id = type_id_to_int(field["group"]["typeId"])
-            group_info = registry.get(group_type_id)
-            if group_info is not None:
-                type_str = group_info.scoped_name
-                if disc_value != _NO_DISCRIMINANT:
-                    union_fields.append((field_name, type_str))
-                else:
-                    non_union_fields.append((field_name, type_str))
+            # Groups become inner classes — skip field annotation
+            # (the group class serves as both type and accessor)
+            pass
 
     # ── class: main type ───────────────────────────────────────────────
     # Generic type: generate TypeVars and Generic[T] base
@@ -225,7 +220,6 @@ def _generate_union_methods(
     emitter: Emitter, union_fields: list[tuple[str, str]],
 ) -> None:
     emitter.add_typing_import("Literal")
-    emitter.add_typing_import("overload")
 
     literal_values = ", ".join(f'"{name}"' for name, _ in union_fields)
     emitter.add_method(
@@ -233,8 +227,12 @@ def _generate_union_methods(
         return_type=f"Literal[{literal_values}]",
     )
 
+    if len(union_fields) > 1:
+        emitter.add_typing_import("overload")
+
     for field_name, type_str in union_fields:
-        emitter.add_decorator("overload")
+        if len(union_fields) > 1:
+            emitter.add_decorator("overload")
         emitter.add_method(
             "init",
             params=["self", f'name: Literal["{field_name}"]'],

src/capnp_stubgen/plugin.py

@@ -197,8 +197,6 @@ def _resolve_cross_imports(
                     break
 
             all_imports.append(tname)
-            if ref_info and ref_info.kind == "struct":
-                all_imports.extend([f"{tname}Builder", f"{tname}Reader"])
 
         emitter.add_import(
             f"from .{module_name} import {', '.join(all_imports)}"