detect owner codex bad request loops

src/codex-bad-request-signal.ts

@@ -0,0 +1,7 @@
+export const CODEX_BAD_REQUEST_DETAIL_JSON = '{"detail":"Bad Request"}';
+
+export function isCodexBadRequestText(
+  text: string | null | undefined,
+): boolean {
+  return text?.trim() === CODEX_BAD_REQUEST_DETAIL_JSON;
+}