Fill in login / avatar_url on clusters. Noreply emails resolve
offline; the rest are looked up via the commits API (one representative
commit per cluster), in parallel.
Clean up the free-text GitHub company field into a usable group name.
Handles common patterns like “@seqeralabs”, “QBiC @qbicsoftware”, and
multi-affiliation strings (“Seqera | SciLifeLab” → “Seqera”).