mcp(fix[option_tools]): Validate scope parameter

why: Invalid scope silently fell through to server scope, making it
impossible for users to detect typos like "global" vs "server".
what:
- Check _SCOPE_MAP.get() result, raise ToolError if scope is invalid
- Add test for invalid scope

Author: tony

src/libtmux/mcp/tools/option_tools.py

@@ -36,6 +36,13 @@ def _resolve_option_target(
     server = _get_server(socket_name=socket_name)
     opt_scope = _SCOPE_MAP.get(scope) if scope is not None else None
 
+    if scope is not None and opt_scope is None:
+        from fastmcp.exceptions import ToolError
+
+        valid = ", ".join(sorted(_SCOPE_MAP))
+        msg = f"Invalid scope: {scope!r}. Valid: {valid}"
+        raise ToolError(msg)
+
     if target is not None and opt_scope is not None:
         if opt_scope == OptionScope.Session:
             return _resolve_session(server, session_name=target), opt_scope

tests/mcp/test_option_tools.py

@@ -5,6 +5,9 @@
 import json
 import typing as t
 
+import pytest
+from fastmcp.exceptions import ToolError
+
 from libtmux.mcp.tools.option_tools import set_option, show_option
 
 if t.TYPE_CHECKING:
@@ -25,6 +28,16 @@ def test_show_option(mcp_server: Server, mcp_session: Session) -> None:
     assert "value" in data
 
 
+def test_show_option_invalid_scope(mcp_server: Server, mcp_session: Session) -> None:
+    """show_option raises ToolError on invalid scope."""
+    with pytest.raises(ToolError, match="Invalid scope"):
+        show_option(
+            option="base-index",
+            scope="global",
+            socket_name=mcp_server.socket_name,
+        )
+
+
 def test_set_option(mcp_server: Server, mcp_session: Session) -> None:
     """set_option sets a tmux option."""
     result = set_option(