Default interactive CLI to menu

src/plugin_helper/cli.py

@@ -70,7 +70,7 @@ def _add_common(parser: argparse.ArgumentParser, *, suppress_default: bool = Fal
 def build_parser() -> argparse.ArgumentParser:
     parser = argparse.ArgumentParser(prog="plugin-helper")
     _add_common(parser)
-    subcommands = parser.add_subparsers(dest="command", required=True)
+    subcommands = parser.add_subparsers(dest="command")
 
     subcommands.add_parser(
         "instances",
@@ -309,6 +309,13 @@ def run(argv: list[str] | None = None) -> int:
     args = parser.parse_args(argv)
 
     try:
+        if args.command is None:
+            if sys.stdin.isatty() and sys.stdout.isatty():
+                args.command = "menu"
+            else:
+                parser.print_help()
+                return 2
+
         explicit_instances_root = getattr(args, "instances_root", None) is not None
         explicit_state_dir = getattr(args, "state_dir", None) is not None
         runtime = resolve_runtime_config(