Add config validation, remove command, status filtering, and unlock method display

config check: validates UUID format, recognized methods, keyfile
consistency and existence. Reports all issues with alias context.

remove: deletes a device from config by alias. Inverse of add.

status: --mounted, --unlocked, --locked flags filter the device table.
Flags combine as OR.

mount/unlock: display which method succeeded and key slot used, e.g.
"(fido2, key slot 1)". cryptsetup Open now runs with -v and parses
"Key slot N unlocked" from stderr via io.MultiWriter.

Co-Authored-By: Claude Opus 4.6 (1M context) <noreply@anthropic.com>

cmd/mount.go

@@ -85,36 +85,43 @@ func runMount(cmd *cobra.Command, args []string) error {
 		return err
 	}
 
+	methodInfo := formatMethod(result)
+
 	if result.Privileged {
 		mnt, err := cryptsetup.Mount(result.Device.DevicePath, mp)
 		if err != nil {
 			return fmt.Errorf("mounting: %w", err)
 		}
-		fmt.Println(mnt)
+		fmt.Printf("%s %s\n", mnt, methodInfo)
 		return nil
 	}
 
 	if mp != "" {
 		fmt.Fprintf(os.Stderr, "warning: --mountpoint is ignored for udisks2 mounts (passphrase/keyfile path)\n")
 	}
-	return doMount(client, result.Device, "")
+	return doMountWithInfo(client, result.Device, "", methodInfo)
 }
 
 func doMount(client *udisks.Client, cleartext *udisks.BlockDevice, mp string) error {
+	return doMountWithInfo(client, cleartext, mp, "")
+}
+
+func doMountWithInfo(client *udisks.Client, cleartext *udisks.BlockDevice, mp, methodInfo string) error {
+	var mnt string
+	var err error
 	if mp != "" {
-		// udisks2 doesn't support custom mount points; use privileged mount.
-		mnt, err := cryptsetup.Mount(cleartext.DevicePath, mp)
-		if err != nil {
-			return fmt.Errorf("mounting: %w", err)
-		}
-		fmt.Println(mnt)
-		return nil
+		mnt, err = cryptsetup.Mount(cleartext.DevicePath, mp)
+	} else {
+		mnt, err = client.Mount(cleartext)
 	}
-	mnt, err := client.Mount(cleartext)
 	if err != nil {
 		return fmt.Errorf("mounting: %w", err)
 	}
-	fmt.Println(mnt)
+	if methodInfo != "" {
+		fmt.Printf("%s %s\n", mnt, methodInfo)
+	} else {
+		fmt.Println(mnt)
+	}
 	return nil
 }