In the port forwarding docs, we warn users about configuring hostnames >63 characters long.

There is a DNS limitation where each segment of hostnames must not exceed 63 characters. If your app name, agent name, workspace name and username exceed 63 characters in the hostname, port forwarding via the dashboard will not work.

We raise a build error if the workspace name + agent name + username exceeds this limit, but there is no warning on coder_app ports where the added app name breaks the limit. Currently, the app fails silently and returns an empty response. We should show that the app is failing due to this character limitation with a health status or an error on the workspace page.