optional: nicer apollo errors for lightning users

[taylordowns2000]

Description

This PR makes it possible to show more detailed errors to AI chat users. Right now, all a user ever sees (regardless of whether the error is related to billing, AI service provides, or anything else) is this:

Validation steps

1. Boot up lightning with a faulty AI assistant token.
2. Try to send a message to the AI chat.
3. See a nicer error.

AI Usage

Please disclose whether you've used AI anywhere in this PR (it's cool, we just
want to know!):

• I have used Claude Code
• I have used another model
• I have not used AI

You can read more details in our
Responsible AI Policy

Pre-submission checklist

• I have performed an AI review of my code (we recommend using /review
  with Claude Code)
• I have implemented and tested all related authorization policies.
  (e.g., :owner, :admin, :editor, :viewer)
• I have updated the changelog.
• I have ticked a box in "AI usage" in this PR

[lmac-1]

@theroinaochieng another one that need clarity on how to prioritise/move forward. Not sure if this belongs in an issue that references this PR as an idea for the solution. And then we can prioritise with the issue.

[taylordowns2000]

@theroinaochieng another one that need clarity on how to prioritise/move forward. Not sure if this belongs in an issue that references this PR as an idea for the solution. And then we can prioritise with the issue.

Thanks for asking, @lmac-1 . It's possible that this was simply missed during the recent re-implementation, or possible that it was actively de-prioritized. I've updated the description to include this image

@theroinaochieng will know 😄