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_windows.go

@@ -0,0 +1,13 @@
+package dbus
+
+import "os"
+
+const defaultSystemBusAddress = "tcp:host=127.0.0.1,port=12434"
+
+func getSystemBusPlatformAddress() string {
+	address := os.Getenv("DBUS_SYSTEM_BUS_ADDRESS")
+	if address != "" {
+		return address
+	}
+	return defaultSystemBusAddress
+}