assistant: Add `diagnostics` slash command (#12998)

This adds a `diagnostics` command to the assistant which allows to
inject compile errors/warnings into the context.

Release Notes:

- N/A
0d8e6e6b12Bennet Bo Fenner committed on 6/14/2024, 3:14:50 PM· committed by GitHubparentbf03f66
12 files changedLine totals unavailable