Filter JSON delimiters from cbftp raw output

[Khazaztroph]

What changed

• Ignore standalone JSON object and array delimiters while parsing cbftp /raw responses.
• Preserve brackets that are part of the actual FTP command output.

Why

The line-oriented parser treated the closing } and ] lines from a valid cbftp JSON response as command output. This displayed JSON syntax in the d-tool window. A broad bracket filter also suppresses legitimate FTP output such as SITE STAT fields, so this change only filters lines that consist solely of a delimiter after spaces are removed.

Validation

Verified with /dcb ioFTPD stat against FluxFTP's cbftp-compatible HTTPS API. The FTP response remains visible while the trailing JSON delimiters are removed.