Remove credential passing to sandboxes (didn't work well enough).
Move onboarding config init from host-side setup into base.nix so
each workspace initializes its own Claude config on first boot.
Wrap claude command in VM and Incus workspaces to always skip
permission prompts.
- Add incus.nix module for fully declarative Incus/LXC containers
- Build NixOS LXC images using nixpkgs.lib.nixosSystem
- Ephemeral containers: recreated on each start, cleaned up on stop
- Use flock to serialize concurrent container operations
- Deterministic MAC addresses via lib.mkMac to prevent ARP cache issues
- Add veth* to NetworkManager unmanaged interfaces
- Update CLAUDE.md with coding conventions and shared lib docs
