Add provider-side seam schema validation CI using rerum_openapi workflow

[cubap]

Implement provider-side contract schema validation in rerum_server_nodejs so CI verifies runtime behavior against seam baselines in cubap/rerum_openapi.

Context

• Contract source of truth is in cubap/rerum_openapi.
• Reusable workflow now exists for provider/consumer harnesses:
  https://github.com/cubap/rerum_openapi/blob/main/.github/workflows/seam-runtime-validation.yml
• Runtime validator now supports:
  1. path coverage
  2. operation and response-code coverage
  3. fixture request/response body validation against OpenAPI schemas

Provider Implementation Plan

1. Add a provider CI workflow in this repo that calls:
   uses: cubap/rerum_openapi/.github/workflows/seam-runtime-validation.yml@main
2. Pin inputs for this provider:
   • contract_repo_ref: main (or pinned tag/commit)
   • seam_manifest_path: seams/tinynode-to-rerum/manifest.yaml (and/or deer-to-rerum, tpen-services-to-rerum, etc. as phased jobs)
   • target_base_url: deployed provider URL for CI environment
   • compare_paths: true
   • compare_operations: true
3. Add a provider fixture file in this repo for representative interactions and pass it with fixture_file.
4. Run this gate on pull_request and push to main; block merge on failure.

Suggested Acceptance Criteria

• CI fails if provider health/readiness/spec endpoints fail for the seam test endpoints.
• CI fails if provider OpenAPI misses expected paths, operations, or response codes from seam baseline.
• CI fails if provider fixture request/response bodies violate baseline schemas.
• CI passes with deterministic fixture data and stable environment config.

Notes

• This adds local deterministic contract gates without introducing a hosted validation service dependency.
• Follow-up optimization can pin contract_repo_ref to release tags instead of main.

[cubap]

Starter workflow snippet to paste into this repo:

name: Provider Contract Validation

on:
pull_request:
push:
branches:
- main

jobs:
validate-tinynode-to-rerum:
uses: cubap/rerum_openapi/.github/workflows/seam-runtime-validation.yml@main
with:
contract_repo_ref: main
seam_manifest_path: seams/tinynode-to-rerum/manifest.yaml
target_base_url: https://store.rerum.io/v1
compare_paths: true
compare_operations: true
fixture_file: test/contract-fixtures/tinynode-to-rerum.yaml
timeout_ms: 10000

If this repo should validate multiple seams, add one job per seam manifest for clearer failure isolation.