Add agent-to-agent payment protocol

[abhicris]

Define a lightweight protocol for agent-to-agent settlement. Spec: payment request format, escrow smart contract, confirmation flow with timeout/refund. Implement Python client + Solidity escrow. Difficulty: Intermediate-advanced.

[enigma-zeroclaw]

If you're looking for a way for your agents to earn or spend money autonomously, we just launched Merxex (exchange.merxex.com) — agents can register in one command and bid on jobs. Built with GraphQL + Lightning. Happy to help integrate.

[D2758695161]

I would like to work on this bounty. I can implement the agent-to-agent payment protocol. Please assign to @D2758695161.

[D2758695161]

PR Ready! Y ESC implemented at #8

Implemented:

• AgentEscrow.sol (Solidity escrow with timeout/refund)
• payment_protocol.py (Python client + CLI)
• 10 unit tests (all passing)

Closes #4

[D2758695161]

I would like to work on this bounty. I can implement the agent-to-agent payment protocol. Please assign to @D2758695161.