When CLAW402_WALLET_KEY env var is set, all nofxos.ai data API calls
(AI500, OI rankings, NetFlow, price rankings) are automatically routed
through claw402.ai with x402 USDC micropayment.
- provider/nofxos/claw402.go: x402 GET request client for data APIs
- provider/nofxos/client.go: claw402 mode support in doRequest()
- kernel/engine.go: auto-detect CLAW402_WALLET_KEY and enable routing
- mcp/payment/x402.go: MakeClaw402SignFunc helper
Without CLAW402_WALLET_KEY, falls back to direct nofxos.ai (backward compat).