Add troubleshooting documentation for Terminus issue with Apple OpenSSH on macOS 15.5, May 2025 and later

[markmont]

Here’s what I just sent out to my customers:

Heads up for people using terminus on macOS to manage their Pantheon sites:

We now have two cases where people encountered problems running terminus drush , terminus wp , terminus composer , terminus logs , and terminus rsync on macOS 15.5. It looks like back in May, Apple updated OpenSSH to be OpenSSH_9.9p2, LibreSSL 3.3.6 with a date of May 4, 2025. This new version of SSH causes these terminus commands to hang if an environment is uninitialized or a site is frozen. A workaround is to install OpenSSH from Homebrew using the command brew install openssh

This problem won’t affect most people in most situations, but since it has now come up twice — and took significant time and effort to troubleshoot in each case — I wanted to give everyone a heads-up just in case.

The problem appears to be that Apple's OpenSSH tries to connect to hostnames that do not actually exist in DNS, and then hangs forever. Homebrew's OpenSSH correctly gives the error "no such host".

[markmont]

For additional detais, see
https://pantheon-community.slack.com/archives/C2GJ3JG7Q/p1748040687087649