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/modules.txt

@@ -0,0 +1,23 @@
+# github.com/godbus/dbus/v5 v5.2.2
+## explicit; go 1.20
+github.com/godbus/dbus/v5
+# github.com/inconshreveable/mousetrap v1.1.0
+## explicit; go 1.18
+github.com/inconshreveable/mousetrap
+# github.com/spf13/cobra v1.10.2
+## explicit; go 1.15
+github.com/spf13/cobra
+# github.com/spf13/pflag v1.0.9
+## explicit; go 1.12
+github.com/spf13/pflag
+# golang.org/x/sys v0.42.0
+## explicit; go 1.25.0
+golang.org/x/sys/plan9
+golang.org/x/sys/unix
+golang.org/x/sys/windows
+# golang.org/x/term v0.41.0
+## explicit; go 1.25.0
+golang.org/x/term
+# gopkg.in/yaml.v3 v3.0.1
+## explicit
+gopkg.in/yaml.v3