feat(sdk): add RIP-302 agent economy client

[bcabreraike-cmyk]

Summary

• add a JavaScript client for the RIP-302 agent-economy marketplace endpoints
• cover job listing, posting, claiming, delivery, acceptance, disputes, cancellation, reputation, and stats
• preserve server response envelopes so pagination and payment metadata remain available

Testing

• node --test — 14 passing
• git diff --check — clean

BCOS Checklist

• Tier label: BCOS-L1
• Tests included
• No production-chain calls were made

Addresses the JavaScript/TypeScript SDK item in #683.

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