- Add nix-shared Incus profile on ThinkStation (bind /data/nix -> /nix)
- Apply nix-shared profile to NixOS VMs on ThinkStation
- coder.nix: disable VM nix-daemon/socket, use host daemon socket
- coder.nix: trusted-users includes workspace user
- coder.nix: override /nix/store fstab to bind from host-mounted /nix