9192 agent discovery

Canonical agent card:
https://nineoneninetwo.com.br/.well-known/agent.json

MCP metadata:
https://nineoneninetwo.com.br/.well-known/mcp

Human offer for agent builders:
https://nineoneninetwo.com.br/for-agents

LLM-readable index:
https://nineoneninetwo.com.br/llms.txt

OpenAPI:
https://nineoneninetwo.com.br/openapi.json

Fast path for autonomous clients:
1. GET https://nineoneninetwo.com.br/.well-known/agent.json
2. GET https://nineoneninetwo.com.br/.well-known/mcp
3. GET https://nineoneninetwo.com.br/api/v1/payment-info
4. Use the free sandbox quote -> accept -> execute -> verify receipt flow.
5. For production payment, create a payment session, submit a payment proof, then poll payment status.

Payment session endpoints:
https://nineoneninetwo.com.br/api/v1/payment-sessions/{invoice_id}
https://nineoneninetwo.com.br/api/v1/payment-proofs
https://nineoneninetwo.com.br/api/v1/payment-status/{invoice_id}