Adapt cmliu/CF-Workers-WebSSH b0265afcaf40681066d24cd5d859dc32d73c8863 without importing unrelated network-monitoring changes. Classify asynchronous read-loop failures, stop retries on control messages or close code 4001, and preserve manual reconnect and auxiliary-channel behavior. Add focused backend, reconnect, and browser regressions; accept CRLF in the existing deployment workflow test.
