style(server.py): format if statement for better readability and maintainability

Author: tumf

src/mcp_shell_server/server.py

@@ -100,10 +100,11 @@ async def run_tool(self, arguments: dict) -> Sequence[TextContent]:
 
             # Add stderr if present and not a process group message
             stderr = result.get("stderr")
-            if stderr and not stderr.startswith("bash: cannot set terminal process group"):
+            if stderr and not stderr.startswith(
+                "bash: cannot set terminal process group"
+            ):
                 content.append(TextContent(type="text", text=stderr))
 
-
         except asyncio.TimeoutError as e:
             raise ValueError(f"Command timed out after {timeout} seconds") from e