fix(test): address code review feedback for ai_gateway tests

Co-authored-by: CBenoit <3809077+CBenoit@users.noreply.github.com>

Author: Copilot

testsuite/tests/cli/dgw/ai_gateway.rs

@@ -27,17 +27,23 @@ async fn spawn_mock_openai_server(response_body: &str) -> SocketAddr {
                 let mut content_length = 0;
                 let mut received_auth_header = String::new();
 
-                // Read HTTP headers.
+                // Read HTTP headers (malformed headers are silently ignored in this test helper).
                 loop {
                     let mut line = String::new();
-                    if reader.read_line(&mut line).await.unwrap() == 0 {
+                    if reader.read_line(&mut line).await.unwrap_or(0) == 0 {
                         break;
                     }
                     if line.to_lowercase().starts_with("content-length:") {
-                        content_length = line.trim().split(':').nth(1).unwrap().trim().parse().unwrap_or(0);
+                        content_length = line
+                            .split_once(':')
+                            .and_then(|(_, v)| v.trim().parse().ok())
+                            .unwrap_or(0);
                     }
                     if line.to_lowercase().starts_with("authorization:") {
-                        received_auth_header = line.trim().split(':').nth(1).unwrap().trim().to_owned();
+                        received_auth_header = line
+                            .split_once(':')
+                            .map(|(_, v)| v.trim().to_owned())
+                            .unwrap_or_default();
                     }
                     if line.trim().is_empty() {
                         break;
@@ -150,9 +156,6 @@ async fn make_ai_request(
     auth_header: Option<&str>,
     body: Option<&str>,
 ) -> anyhow::Result<(u16, String)> {
-    let listener = TcpListener::bind("127.0.0.1:0").await?;
-    drop(listener); // Just to check port binding works.
-
     let stream = tokio::net::TcpStream::connect(format!("127.0.0.1:{gateway_port}")).await?;
     let (mut reader, mut writer) = stream.into_split();
 
@@ -197,7 +200,10 @@ async fn make_ai_request(
                         .lines()
                         .find(|l| l.to_lowercase().starts_with("content-length:"))
                     {
-                        let cl: usize = cl_line.split(':').nth(1).unwrap().trim().parse().unwrap_or(0);
+                        let cl: usize = cl_line
+                            .split_once(':')
+                            .and_then(|(_, v)| v.trim().parse().ok())
+                            .unwrap_or(0);
                         let body_start = headers_end + 4;
                         if response.len() >= body_start + cl {
                             break;