Classify a single event, or reweight one already classified, then rescore.

Creates the row when it is missing, which it previously refused with a 404. The classifier only ever sees product_context.raw_event_names, snapshotted at import, so an event a workspace ships AFTER setup is never classified and there was no way to classify one: the only paths were reweighting a row that already existed, or re-running the whole classifier off that same stale list. Measured on Parrot 2026-09-03: 159 of the top 400 events had no row, carrying 11.9% of 30-day volume, including streak_day at 37,013 events.

That is not cosmetic, because weight > 0 is what event_extract_job selects on. An unclassified event never reaches customer_events, so nothing reading that table can see it — which is why the streak programme ran entirely on its property fallback (from_events: 0) and could not tell whether somebody had already practised today.

category is required on a create because the column is NOT NULL and readers branch on its exact value; on an update it stays optional.