chore: drop full error stack traces from chat error logs

Shorten the ✗ ERROR 502 / stream ERROR lines to the message only; the
multi-KB next-dev stack trace polluted the console on every provider error.

open-sse/handlers/chatCore.js

@@ -422,7 +422,7 @@ export async function handleChatCore({ body, modelInfo, credentials, log, onCred
     }
     const errMsg = formatProviderError(error, provider, model, HTTP_STATUS.BAD_GATEWAY);
     if (log?.errorLine) {
-      log.errorLine(reqTag, "✗", `ERROR 502 · ${provider}/${model} · ${Date.now() - requestStartTime}ms\n    ${errMsg}${error.stack ? `\n    ${error.stack}` : ""}`);
+      log.errorLine(reqTag, "✗", `ERROR 502 · ${provider}/${model} · ${Date.now() - requestStartTime}ms\n    ${errMsg}`);
     }
     return createErrorResult(HTTP_STATUS.BAD_GATEWAY, errMsg, error?.resetsAtMs || undefined);
   }

open-sse/utils/streamHandler.js

@@ -78,7 +78,7 @@ export function createStreamController({ onDisconnect, onError, log, provider, m
         return;
       }
 
-      logStream("✗", `ERROR: ${error.message}${error.stack ? `\n    ${error.stack}` : ""}`, true);
+      logStream("✗", `ERROR: ${error.message}`, true);
       onError?.(error);
     },