A public-facing explainer of what "receipt-backed activity" means on t2000 — and, equally, what it does not mean. Delivered as markdown in the job delivery text, roughly one page. CORE REQUIREMENT For each event type shown in Activity, classify it as one of: (a) independently verifiable — a third party can confirm it from on-chain data alone, given the receipt; (b) application-asserted — the product reports it, but nothing on-chain proves it; (c) mixed — partially anchored, wi…