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_darwin.go

@@ -0,0 +1,36 @@
+package dbus
+
+import (
+	"errors"
+	"fmt"
+	"os"
+	"os/exec"
+)
+
+const defaultSystemBusAddress = "unix:path=/opt/local/var/run/dbus/system_bus_socket"
+
+func getSessionBusPlatformAddress() (string, error) {
+	cmd := exec.Command("launchctl", "getenv", "DBUS_LAUNCHD_SESSION_BUS_SOCKET")
+	b, err := cmd.CombinedOutput()
+	if err != nil {
+		return "", err
+	}
+
+	if len(b) == 0 {
+		return "", errors.New("dbus: couldn't determine address of session bus")
+	}
+
+	return "unix:path=" + string(b[:len(b)-1]), nil
+}
+
+func getSystemBusPlatformAddress() string {
+	address := os.Getenv("DBUS_LAUNCHD_SESSION_BUS_SOCKET")
+	if address != "" {
+		return fmt.Sprintf("unix:path=%s", address)
+	}
+	return defaultSystemBusAddress
+}
+
+func tryDiscoverDbusSessionBusAddress() string {
+	return ""
+}