ChainLedgerAI: On-Chain Metrics API

Pulling real activity metrics for an Ethereum address usually means writing and tuning BigQuery SQL against the public crypto_ethereum dataset yourself — workable, but slow to get right and easy to accidentally run an expensive query on. ChainLedgerAI wraps that dataset in a simple API: give it an address, get back transaction counts, volume, counterparty count, activity windows, and an activity-frequency label — plus an optional AI-generated plain-English summary. Every query call takes a max_bytes_billed ceiling, so there's no surprise cost. Ethereum mainnet only today. This is read-only factual data — it does not return a risk score, compliance flag, or AML/sanctions judgment, and never will (that's a hard rule, not a roadmap gap — see CONTRIBUTING.md in the public repo). Free tier: 1,000 calls/day. Growth: $49/month for 50,000/day. Scale: $199/month for 500,000/day.