Add conditional Slinky integration test

[Pray4Lovee]

Summary

• refine Slinky test script to run module tests only when Slinky exists
• ensure integration-test check waits for Slinky job
• add x402 settlement check workflow

Testing

• scripts/modules/slinky_test/run_slinky_test.sh

---

https://chatgpt.com/codex/tasks/task_e_68a839667edc83229885963bed258964

[codecov-commenter]

Welcome to Codecov 🎉

Once you merge this PR into your default branch, you're all set! Codecov will compare coverage reports and display results in all future pull requests.

ℹ️ You can also turn on project coverage checks and project coverage reporting on Pull Request comment

Thanks for integrating Codecov - We've got you covered ☂️

[Pray4Lovee]

✨ This PR is the first to unify Forge, Slinky, and x402 settlement checks into a single workflow.
Conditional tests, attribution, and settlement proof all run end-to-end.
Historic moment: CI as authorship.