Address the remaining review comments

inky/opts.go

@@ -12,7 +12,7 @@ import (
 )
 
 var (
-	displayVariantMap = []string{
+	displayVariantMap = [...]string{
 		"",
 		"Red pHAT (High-Temp)",
 		"Yellow wHAT",

inky/types.go

@@ -1,6 +1,7 @@
 // Copyright 2023 The Periph Authors. All rights reserved.
 // Use of this source code is governed under the Apache License, Version 2.0
 // that can be found in the LICENSE file.
+
 package inky
 
 //go:generate stringer -type=Model,Color,ImpressionColor -output types_string.go