Handle SSH config conflicts better

~I think we will need to prepend the config to avoid being clobbered by `Host *` configs further up in the stack.~ If we prepend it needs to be via an include to avoid clobbering any global settings not under a host block at the top.

But we should also change the host name because it is probably not uncommon to have a `*.mycompany.com` entry. We could prepend the URL or swap it with the agent name. Or obfuscate the domain in some way.