style: restore trailing newline in main.rs (fix CI format gate)

The await_holding_lock allow attributes were patched in without a final newline, which cargo fmt --check (and the release parity job) rejected. Restoring it.

Author: Hmbown

crates/tui/src/main.rs

@@ -9052,4 +9052,4 @@ mod pr_prompt_tests {
             "missing command should return false, not panic"
         );
     }
-}
+}