docs: align runtime and contributor guides with implementation

[sbalabanov]

Summary

Intent:

• Keep runtime and contributor documentation aligned with the current service topology and workflows.
• Correct only clear implementation deviations while leaving historical RFCs unchanged.

Changes:

• Document the current SubmitQueue, Runway, and Stovepipe service wiring, configuration, queue stages, and shutdown behavior.
• Correct test locations, Bazel labels, queue payload examples, Compose naming guarantees, and Gateway grpcurl guidance.

---

_{Generated by the 🪄 pr-create skill in devexp-agent-marketplace}

Test Plan

Issues

[CLAassistant]

Thank you for your submission! We really appreciate it. Like many open source projects, we ask that you sign our Contributor License Agreement before we can accept your contribution.
_{You have signed the CLA already but the status is still pending? Let us recheck it.}