Display an error state when GitLab Duo Chat can't be reached

Problem

GitLab Duo Chat can appear to be functional until a user sends a prompt. This was particularly obvious during an incident that resulted in A1001 errors. It would be nice to ask Duo Chat whether it is operating reliability or whether there is an incident on .com. Duo Chat could respond with the knowledge about GitLab that it already has, either by using our status pages or checking its own health. One solution might be to proactively show the status of Duo Chat or GitLab as a whole as degraded, without the user having to ask the question to Duo Chat.

Default	After prompt

Proposal

When the Duo Chat panel is opened, make sure that it passes the connection check. If it fails, then send an error message through the prop. Ideally, the input buttons would also be disabled.

Empty state with error	Conversation history with error