Phase 6: Support distributed validation across multiple developers

[nakurian]

Problem

When two developers work on different services (e.g., UI expert on web-ui, backend expert on order-service), Phase 6 (Validate) assumes all services are available locally on one machine. This breaks in real multi-developer workflows.

Scenarios to support

1. Dev A has UI, Dev B has backend — validation needs both services running. Currently no way to point at a remote service.
2. Shared dev environment — services deployed to a shared dev/staging cluster where validation can run against real URLs.
3. Docker compose across local builds — one developer pulls the other's image from a registry instead of building locally.

Proposed solution

Add a validation section to manifest.yaml per service:

services:
  - name: "order-service"
    validation:
      strategy: "local"          # local | remote | docker-image
      remote_url: ""             # if remote: http://dev.internal:5001
      docker_image: ""           # if docker-image: ghcr.io/org/order-service:latest

The validate phase should:

• Check each service's validation.strategy
• For local: use local_path and start via docker-compose
• For remote: use the remote_url directly (skip docker-compose for this service)
• For docker-image: pull and run the image instead of building from source
• Generate a docker-compose.yaml that mixes local builds and remote images

Additional considerations

• The validate phase should support a "contract-only" mode where it validates contracts without running services (for when not all services are available)
• Add guidance for setting up a shared dev environment URL in manifest.yaml environments section
• Consider integration with Testcontainers for spinning up dependencies