We rely on temporarily setting ZDOTDIR to our `zsh` resource directory
to implement automatic shell integration. Setting ZDOTDIR in a system
file like /etc/zshenv overrides our ZDOTDIR value, preventing our shell
integration from being loaded.
The only way to prevent /etc/zshenv from being run is via the --no-rcs
flag. (The --no-globalrcs only applies to system-level files _after_
/etc/zshenv is loaded.) Unfortunately, there doesn't appear to be a way
to run a "bootstrap" script (to reimplement the Zsh startup sequence
manually, similar to how our bash integration works) and then enter an
interactive shell session.
https://zsh.sourceforge.io/Doc/Release/Files.html
Given all of the above, document this as an unsupported configuration
for automatic shell integration and point affected users at our manual
shell integration option.