"Debug Run" option

It’d be great if we could pause a run, or stop it from exiting, in order to debug any issues that might be happening in a particular step. I know we can get pretty much the full context from the “Environment” tab, but once the build is done/fails, the agent returns to the pool and can pick up another build, resulting in the context being potentially deleted.

It’s a pretty common feature is hosted CI providers for something similar to this, and it’d be awesome to see it in buildkite too.

tl;dr - Temporarily stop an agent accepting new jobs so I can debug the current context