- find_docker() now checks HERMES_DOCKER_BINARY env var first, then
docker on PATH, then podman on PATH, then macOS known locations
- Entrypoint respects HERMES_HOME env var (was hardcoded to /opt/data)
- Entrypoint uses groupmod -o to tolerate non-unique GIDs (fixes macOS
GID 20 conflict with Debian's dialout group)
- Entrypoint makes chown best-effort so rootless Podman continues
instead of failing with 'Operation not permitted'
- 5 new tests covering env var override, podman fallback, precedence
Based on work by alanjds (PR #3996) and malaiwah (PR #8115).
Closes#4084.