Delegating a GitHub issue works on repositories with capital letters

We store every repository name in lowercase, but GitHub reports it in the case you registered it with. The dashboard recorded who clicked under the lowercase name, and the webhook that GitHub sent back looked for it under the original case, so the two never matched. On a repository like Acme-Corp/Widget the issue got assigned and labelled and then nothing else happened: the spinner ran out and the task list stayed empty. Repositories whose names are already lowercase were unaffected.

Both sides now agree on one spelling. The same mismatch also kept an issue that was already running from being hidden in the picker, so it could be offered twice; that is fixed too.