enhancement request: add health checks to coder_agent apps (VS Code Desktop, Terminal, VS Code Insiders)

At present the app buttons which are made available on a workspace do not have health checks, as a result the buttons can be clicked immediately upon a workspace being created and while the workspace is yet to be in a ready state.

A customer has reported this as their userbase has been experiencing failures with VS Code Desktop to connect when the workspace is not ready.

Given other apps/modules/resources support health checks and operate on TCP the idea is to bring parity to the built in apps such as Terminal & VS Code Desktop.