fix: always strip old functionCall/functionResponse from LS history

The function call stripping was only happening when no custom tools
were present. But even with custom tools injected, the LS history
contains functionCall/functionResponse parts for LS-internal tools
that we stripped, causing MALFORMED_FUNCTION_CALL. Now always strip
regardless of custom tools presence.

src/mitm/proxy.rs

@@ -726,6 +726,12 @@ async fn handle_http_over_tls(
                     }
                     headers_parsed = true;
 
+                    // Log error response bodies for debugging
+                    if resp.code.unwrap_or(0) >= 400 {
+                        let body_preview = String::from_utf8_lossy(&header_buf[hdr_end..]);
+                        warn!(domain, status = resp.code.unwrap_or(0), body = %body_preview, "MITM: upstream error response");
+                    }
+
                     // Save body for usage parsing
                     response_body_buf.extend_from_slice(&header_buf[hdr_end..]);