Intercept and mock failed SSH connections to provide log dumps, or even a troubleshooting link

首先阅读提案，并追踪扩展当前如何依赖 Coder 的 SSH ProxyCommand 行为。确定失败的连接如何呈现给 VS Code 和 JetBrains 集成，然后定义受支持的诊断消息、hook 或故障排查链接。根据客户报告的失败案例对其进行验证。

This is just an idea and was inspired by a customer-reported issue: https://github.com/coder/coder/issues/11978

Background

Today, Coder already "mocks" real SSH by running ProxyCommand. This is awesome, because Coder sysadmins do not need to open port 22 on devices, but makes it difficult for ssh, VS Code, or other commands to get the full story of why a connection has failed. Some logs are available with coder ssh -v, but in cases like VS Code Remote SSH, paths to get this info are unclear to the user as they just see a "Cannot reconnect. Please reload the window." button

We are working on coder/coder#12160, which will allow admins (or pipelines with admin access) to collect diagnostic information on behalf of a workspace. However, users will not be able to request it, and in the case of #119878 there is an issue external to Coder (e.g. VPN troubleshooting) that is causing the issue.

Proposal

If a connection to a workspace fails, we still "mock" the SSH request so that ssh or IDE plugins (VS Code and JetBrains) think it succeeds and then a message/hook can provide additional logging, or even link to an external wiki/service that gives the user more details on how to resolve/diagnose this issue.

By mocking an SSH connection, it allows us to inform extensions and provide a better UX than VS Code's "disconnected." It could be a useful utility for troubleshooting user connections by supplying more data or custom errors.