feat(MM-66): add nix/docker.nix and expose docker-image on Linux
docs(MM-66): note docker-image is Linux-only in CLAUDE.md
docs(MM-66): add nix/ directory to project structure in CLAUDE.md
test(MM-66): add automated verification script for AC1.3 and AC3.4
docs: add test plan for MM-66 Docker image
docs(MM-66): commit implementation plans and ignore nix result symlink
fix(MM-66): address PR review — verify-mm66.sh silent failures, comments, CLAUDE.md
docs(MM-66): note NixOS Docker sysctl issue in test plan step 4.1