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_default_windows.go

@@ -0,0 +1,5 @@
+package dbus
+
+func getDefaultAuthMethods(user string) []Auth {
+	return []Auth{AuthCookieSha1(user, getHomeDir())}
+}