Add a custom Docker image (foundry-base.Dockerfile) that builds sandbox-agent
from source and layers sudo, git, neovim, gh, node, bun, chromium, and
agent-browser. Includes publish script for timestamped + latest tags to
rivetdev/sandbox-agent on Docker Hub.
Update local sandbox provider default to use foundry-base-latest and wire
HF_LOCAL_SANDBOX_IMAGE env var through compose.dev.yaml.
Co-Authored-By: Claude Opus 4.6 (1M context) <noreply@anthropic.com>
