Get Decision Counts

Counts by status over the whole artifact, zero-filled.

Declared above the parameterised routes on purpose. FastAPI matches in declaration order, so a literal sub-path below /{decision_index} would be swallowed by it and "counts" looked up as a decision index. There is no GET /{decision_index} on this router today, so nothing collides yet — declaring it here is what keeps that true when one is added.

A missing decisions artifact 404s exactly as the list endpoint does, rather than reporting zeros. Zero recorded decisions and no decisions layer are different facts, and only one of them is worth printing as a number. The page is what degrades: it treats an unavailable count as unknown and says what it actually loaded instead, so a frontend running ahead of its backend renders the table rather than "Page not found".