fix(shell_executor.py): correct syntax error in token list by adding a comma between ";" and "&&" to ensure proper parsing of shell operators

Author: tumf

src/mcp_shell_server/shell_executor.py

@@ -269,7 +269,7 @@ def _validate_pipeline(self, commands: List[str]) -> None:
                     raise ValueError("Empty command before pipe operator")
                 self._validate_command(current_cmd)
                 current_cmd = []
-            elif token in [";" "&&", "||"]:
+            elif token in [";" , "&&", "||"]:
                 raise ValueError(f"Unexpected shell operator in pipeline: {token}")
             else:
                 current_cmd.append(token)