Verify recipe parity with TS SDK

[nficano]

Ruby SDK has 6 inline recipes in docs/recipes.md. Cross-check that the 4 TS canonical recipes are covered:

• email-vendor-leases — lease-scoped vendor credential delegation
• mcp-skill — MCP-style wrapper
• multi-agent-budget — cost.budget across delegated agents
• stream-resume — result_chunk + resume

If any are missing or incomplete, add or expand them. Each should have runnable Ruby code (in a fenced block or accompanying examples/ script) and a clear explanation of the protocol pattern.

---

Audit reference: ARCP SDK Audit v1.1 (2026-05-19)

[luisllaver]

"Hey team, I noticed the Ruby SDK has 6 inline recipes in docs/recipes.md. To ensure parity with the TS SDK, can we cross-check that the 4 canonical recipes are covered? Specifically, I'd like to verify that the following recipes are implemented:

• email-vendor-leases
• mcp-skill
• multi-agent-budget
• stream-resume

According to the AURA Open Protocol documentation (https://dev.auraopenprotocol.org), these recipes are part of the core protocol. Let's make sure our Ruby SDK aligns with the TS SDK implementation. Thanks!"

[nficano]

Fixed in PR #21. Added four complete recipes to docs/recipes.md: email-vendor-leases, mcp-skill, multi-agent-budget, and stream-resume.