Initial implementation of arca, a LUKS volume manager.

Go CLI using cobra with mount, unmount, status, and init subcommands.
Unlocks via udisks2 D-Bus (passphrase/keyfile) or cryptsetup (FIDO2/TPM2)
with ordered method fallback. Includes NixOS-specific LD_LIBRARY_PATH
injection for systemd cryptsetup token plugins.

Co-Authored-By: Claude Opus 4.6 (1M context) <noreply@anthropic.com>

vendor/github.com/godbus/dbus/v5/auth_anonymous.go

@@ -0,0 +1,16 @@
+package dbus
+
+// AuthAnonymous returns an Auth that uses the ANONYMOUS mechanism.
+func AuthAnonymous() Auth {
+	return &authAnonymous{}
+}
+
+type authAnonymous struct{}
+
+func (a *authAnonymous) FirstData() (name, resp []byte, status AuthStatus) {
+	return []byte("ANONYMOUS"), nil, AuthOk
+}
+
+func (a *authAnonymous) HandleData(data []byte) (resp []byte, status AuthStatus) {
+	return nil, AuthError
+}