Organize game files into their project directory and ensure proper build configuration

Moves all game source files and assets into the 'American-Identity-Project' directory and updates the manifest to point to the 'Display' class as the main entry point.

Replit-Commit-Author: Agent
Replit-Commit-Session-Id: f6819c21-e85d-45ac-acde-604db2cfa4fe
Replit-Commit-Checkpoint-Type: full_checkpoint
Replit-Commit-Event-Id: a9500e48-7f68-408f-a5c6-28df9f59fe00
Replit-Helium-Checkpoint-Created: true

American-Identity-Project/Display.java

@@ -0,0 +1,21 @@
+import javax.swing.*;
+
+public class Display {
+  public static void main(String[] args) {
+    int boardWidth = 800;
+    int boardHeight = 600;
+    int tileSize = 20;
+
+    JFrame game = new JFrame();
+    game.setDefaultCloseOperation(JFrame.EXIT_ON_CLOSE);
+    game.setSize(boardWidth, boardHeight);
+    game.setVisible(true);
+    game.setLocationRelativeTo(null);
+    game.setResizable(false);
+
+    Platformer platformer = new Platformer(boardWidth, boardHeight, tileSize);
+    game.add(platformer);
+    game.pack();
+    platformer.requestFocus();
+  }
+}