Aligns the project with the current Compose Specification, which
designates compose.yaml as the canonical filename and treats the
docker-compose.yml name as a legacy fallback.
Renames every compose file in the repo (the root dev/e2e stack, the
deployment examples under examples/, and the integration-test infra
stack) and updates all documentation, the integration test runner, the
capability hint messages, and the .gitattributes pattern accordingly.
No top-level version field was present to remove.
Functional behavior is unchanged: docker compose discovers either
filename, so existing deployments are not affected by the rename.
Reference: https://docs.docker.com/compose/intro/compose-application-model/
