fix: add public modifier to gameDir/gameJsonPath for GameStore interface

src/main/java/com/dostalgia/GameService.java

@@ -55,11 +55,11 @@ public class GameService implements GameStore {
 
     // ─── Game Directory Helpers ──────────────────────────────────
 
-    Path gameDir(String id) {
+    public Path gameDir(String id) {
         return gamesDir.resolve(id);
     }
 
-    Path gameJsonPath(String id) {
+    public Path gameJsonPath(String id) {
         return gameDir(id).resolve("game.json");
     }