Done. PR #10066 is up.
Here's what went in (4 files, +96/-11):
**`tools/environments/docker.py`** — `find_docker()` now has a 4-step resolution chain:
1. `HERMES_DOCKER_BINARY` env var (explicit override, e.g. `/usr/bin/podman`)
2. `docker` on PATH
3. `podman` on PATH (automatic fallback)
4. macOS Docker Desktop known locations
**`docker/entrypoint.sh`** — Three fixes for rootless Podman on macOS:
- `HERMES_HOME="${HERMES_HOME:-/opt/data}"` instead of hardcoding
- `groupmod -o -g` tolerates non-unique GIDs (the macOS GID 20 "staff" collision)
- `chown` is best-effort with a warning instead of a hard failure
**Tests** — 5 new tests covering env var override, invalid/nonexistent override fallthrough, podman-when-docker-missing, and docker-preferred-over-podman.
This should unblock the Discord user's immediate problem. The more comprehensive Podman PRs (#8158, #8391) can be evaluated separately for deeper integration.