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>

internal/udisks/mount.go

@@ -0,0 +1,23 @@
+package udisks
+
+import (
+	"fmt"
+)
+
+// Mount mounts a filesystem and returns the mount point chosen by udisks2.
+func (c *Client) Mount(dev *BlockDevice) (string, error) {
+	obj := c.conn.Object(busName, dev.ObjectPath)
+
+	var mountpoint string
+	err := obj.Call(ifaceFilesystem+".Mount", 0, noOptions()).Store(&mountpoint)
+	if err != nil {
+		return "", fmt.Errorf("mounting %s: %w", dev.DevicePath, err)
+	}
+	return mountpoint, nil
+}
+
+// Unmount unmounts a filesystem.
+func (c *Client) Unmount(dev *BlockDevice) error {
+	obj := c.conn.Object(busName, dev.ObjectPath)
+	return obj.Call(ifaceFilesystem+".Unmount", 0, noOptions()).Err
+}