Problem: DELE, RMD, MKD, and RNFR/RNTO were implemented using
curl --quote, which requires a subsequent LIST or STOR to trigger
the FTP connection. That data-channel operation hangs on slow or
busy servers, making every mutation appear stuck.
Solution: replace the curl --quote approach with a python3 ftplib
one-liner for all control-channel operations. ftplib executes DELE,
RMD, MKD, RNFR/RNTO, and SITE CHMOD without opening a data channel,
so they complete instantly. The curl wrapper is retained for LIST,
read_file, and write_file, which genuinely need a data channel.
Problem: canola has no way to browse or edit files on FTP servers,
despite the adapter system being designed for exactly this pattern.
curl speaks FTP natively, including FTPS (FTP over TLS), and requires
no new dependencies.
Solution: implement `lua/oil/adapters/ftp.lua` with `oil-ftp://` and
`oil-ftps://` schemes. Parses Unix and IIS LIST output, supports
`size`, `mtime`, and `permissions` columns, and implements the full
adapter API (list, read_file, write_file, render_action, perform_action).
Same-host renames use RNFR/RNTO; cross-host and local↔FTP copies use
curl download/upload through a tmpfile. Adds `extra_curl_args` config
option and documents the adapter in `doc/oil.txt`.
Based on: stevearc/oil.nvim#210
