Rewrite README with tested examples, config reference table, unlock
method matrix, NixOS-specific notes on LD_LIBRARY_PATH for cryptsetup
token plugins, FIDO2 enrollment instructions, and troubleshooting
section. Verify nix build produces working binary with version injection.
Co-Authored-By: Claude Opus 4.6 (1M context) <noreply@anthropic.com>
