GHSA-xjvp-7243-rg9h: Wish has SCP Path Traversal that allows arbitrary file read/write

The SCP middleware in charm.land/wish/v2 is vulnerable to path traversal attacks. A malicious SCP client can read arbitrary files from the server, write arbitrary files to the server, and create directories outside the configured root directory by sending crafted filenames containing ../ sequences over the SCP protocol.