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/conn_unix.go

@@ -0,0 +1,40 @@
+//go:build !windows && !solaris && !darwin
+
+package dbus
+
+import (
+	"net"
+	"os"
+)
+
+const defaultSystemBusAddress = "unix:path=/var/run/dbus/system_bus_socket"
+
+func getSystemBusPlatformAddress() string {
+	address := os.Getenv("DBUS_SYSTEM_BUS_ADDRESS")
+	if address != "" {
+		return address
+	}
+	return defaultSystemBusAddress
+}
+
+// DialUnix establishes a new private connection to the message bus specified by UnixConn.
+func DialUnix(conn *net.UnixConn, opts ...ConnOption) (*Conn, error) {
+	tr := newUnixTransportFromConn(conn)
+	return newConn(tr, opts...)
+}
+
+func ConnectUnix(uconn *net.UnixConn, opts ...ConnOption) (*Conn, error) {
+	conn, err := DialUnix(uconn, opts...)
+	if err != nil {
+		return nil, err
+	}
+	if err = conn.Auth(conn.auth); err != nil {
+		_ = conn.Close()
+		return nil, err
+	}
+	if err = conn.Hello(); err != nil {
+		_ = conn.Close()
+		return nil, err
+	}
+	return conn, nil
+}