refactor: type subparser protocol

Agent-Logs-Url: https://github.com/ShigureLab/expr-simplifier/sessions/8d74859a-e701-4f8a-97bc-3e7d404c7baa

Co-authored-by: SigureMo <38436475+SigureMo@users.noreply.github.com>

Author: Copilot

src/expr_simplifier/__main__.py

@@ -3,14 +3,18 @@
 import argparse
 import ast
 from collections.abc import Callable
-from typing import Any
+from typing import Any, Protocol
 
 from expr_simplifier import __version__
 from expr_simplifier.transforms import apply_constant_folding, apply_cse, apply_logical_simplification
 from expr_simplifier.typing import Pass
 from expr_simplifier.utils import loop_until_stable
 
 
+class _SubparserFactory(Protocol):
+    def add_parser(self, name: str, /, **kwargs: Any) -> argparse.ArgumentParser: ...
+
+
 def create_pass_command(name: str, passes: list[Pass]) -> Callable[[argparse.Namespace], None]:
     def pass_command(args: argparse.Namespace) -> None:
         expr = ast.parse(args.input, mode="eval")
@@ -25,7 +29,7 @@ def create_pass_parser(
     name: str,
     passes: list[Pass],
     description: str,
-    subparser: Any,
+    subparser: _SubparserFactory,
 ) -> None:
     parser = subparser.add_parser(name, help=description)
     parser.add_argument("input", help="The expression to simplify")