test(oauth): serialize auth path assertions

Take the shared test environment lock while comparing the generated missing-auth message with the active auth-file path. This prevents parallel environment guards from changing the path between the two reads on Windows CI.

Signed-off-by: Nightt <87569709+nightt5879@users.noreply.github.com>

Author: nightt5879

crates/tui/src/oauth.rs

@@ -431,6 +431,7 @@ mod tests {
 
     #[test]
     fn missing_auth_message_mentions_oauth_checked_locations() {
+        let _lock = crate::test_support::lock_test_env();
         let message = missing_auth_message();
 
         assert!(message.contains("OpenAI Codex OAuth credentials not found"));