Buffer.isBuffer or treated payloads as UTF-8, corrupting packets and risking
native aborts (bad_optional_access). Normalize ArrayBuffer views in
SFTP.prototype.data and Protocol channelData/channelExtData; align READ shim.
Also includes earlier SFTP hardening: REQUEST.READ/WRITE/FSETSTAT guards,
enqueueSftpReply(reqid) + FAILURE on handler error, CHANGELOG.