install.sh: host installer omits the xz dependency #72

What happened

The installer checks and installs git, curl, openssl, and zstd, but fresh Node installation extracts a .tar.xz archive without ensuring xz-utils is available.

Reproduction:

1. Start a supported minimal Debian or Ubuntu x86_64 host with no suitable Node installation and no xz executable.
2. Run the current installer unchanged.
3. Observe preflight, package installation, and the Node phase.

Expected: The one-command installer should install every dependency needed to extract and install Node.

Actual: Preflight succeeds and declared packages install, but tar -xJf fails because it cannot execute xz. Node remains absent and installation exits 1.

Impact: Fresh installation fails on supported minimal Debian or Ubuntu hosts that lack the decompressor.

dor doctor output

Not applicable — the installer exits during Node archive extraction before daemon installation and before doctor can run. dor doctor was not run.

Environment

• Dormice commit: 4417ae14938273f5d937c476cf7cdc57e22e53a5
• Install mode: install.sh reproduction on fresh minimal images
• OS: Ubuntu 24.04 amd64 and Debian 12 amd64 slim
• Verification: Verified with the read-only current worktree at 4417ae14938273f5d937c476cf7cdc57e22e53a5 inside amd64 Ubuntu 24.04 and Debian 12 slim environments.