[bdbarnett]

A trailing slash on the folder you upload now means "its contents", as in rsync. mpftp put -r ./cast/ /cast copies the files into /cast (created if missing) and replaces changed files in place, so re-uploading a library no longer nests it as /cast/cast.

Without the slash nothing changes: put -r ./cast /cast still behaves like cp -r. get -r /cast/ ./cast reads the slash the same way, and so does cp between two boards.

Files on the board that the source folder lacks are left alone, as with rsync without --delete. The docs say so and point to mpftp rm.

Updated: put -r / get -r --help, the CLI reference, the file-transfer guide (where the nesting trap was explained) and the changelog.

Tested on an ESP32-P4 over serial: a first upload of 3 files, a re-upload that changed one file, added one and dropped one (the dropped one stayed on the board; the changed file hashed equal to the local copy), and the no-slash form still nested. Fixes #185.