Cloud sandbox: enable Docker daemon for container builds

Context

Solo build of a healthcare-billing SaaS using Claude Code on the web (cloud sessions) for phone-driven development. The cloud sandbox has the Docker CLI installed but dockerd is not running, so docker build, docker run, and Docker Compose stacks are all blocked.

Phase 1 substrate (infrastructure-as-code, GitHub Actions, Bicep) doesn't need container builds locally — they run in Actions, which has its own daemon. But Phase 2+ work, particularly anything around containerized testing, devcontainers, or local Postgres/Redis sidecars, will hit this wall.

Today's workaround

• Container builds happen in GitHub Actions
• Local container experimentation requires a desktop session

What I'd like to know

• Is enabling dockerd in the cloud sandbox technically feasible, or is it already gated behind a config option I haven't found?
• If not, are nested rootless docker / Podman / sysbox-style alternatives viable as a path to container builds?
• Roadmap timing for in-sandbox container support.

If there's a path to enable dockerd (or accept a sidecar daemon socket), a SessionStart hook can handle activation. If no path exists, I'll document the boundary explicitly and stay on the "container work happens in Actions / desktop" workaround.