Thin generic client over the 84-endpoint Surf API: CEX/DEX market data,
on-chain SQL, wallet intelligence, Polymarket + Kalshi prediction markets,
Twitter/CT mindshare, news, VC funds, OpenAI-compatible chat. Three flat
tiers ($0.001 / $0.005 / $0.020), x402-paid in USDC on Base.

Surface deliberately stays at get<T>(path, params?) and post<T>(path, body?)
rather than 84 typed wrappers — leading /v1/surf is auto-prepended, query
arrays serialize as repeated keys, undefined/null params are dropped.

Tests: 10 new unit tests covering URL construction, POST body shape,
402-without-requirements failure path. Full catalog stays at
https://blockrun.ai/marketplace/surf.