fix(runtime): document agent submission ids

[nyxst4ck]

Summary

• Add submissionId to the public agent admission and synchronous invocation response schemas.
• Extend the OpenAPI routing test so both documented agent response modes expose submissionId alongside stream coordinates.

Test Plan

• pnpm --dir packages/runtime exec vitest run test/routing.test.ts
• pnpm --dir packages/runtime run build
• pnpm --dir packages/runtime exec tsc --noEmit
• git diff --check

Fixes #292

[astrobot-houston]

Thanks for the contribution! We're closing this PR and moving the conversation to the issue: #309

We've moved to a model where bugs and feature proposals are discussed in issues/discussions before code review, so the community can help prioritize and shape the work. Your branch is linked from the new thread so the implementation isn't lost — please join us there to continue the conversation.

— astrobot 🤖