Gather the pick key's load and render sides in pick.go, and name each thing for what it is

sorted.go

@@ -10,3 +10,13 @@ func sortedNames[V any](m map[string]V) []string {
 	sort.Strings(names)
 	return names
 }
+
+func join(prefix, name string) string {
+	switch {
+	case prefix == "":
+		return name
+	case name == "":
+		return prefix
+	}
+	return prefix + "." + name
+}