Refactor Ghost mode handling to prioritize mode transitions

Reordered GhostMode enum for logical priority and updated `setMode` to enforce transitions only to higher-priority modes. Added `currentMode` method for determining the Ghost's active mode, ensuring cleaner and safer state management.

src/main/java/se/urmo/game/entities/ghost/Ghost.java

@@ -88,7 +88,10 @@ public class Ghost extends BaseAnimated {
     }
 
     public void setMode(GhostMode mode) {
-        currentState = states.get(mode);
+        GhostMode currentMode = currentMode();
+        if (currentMode == null || mode.ordinal() < currentMode.ordinal()) { // only if new mode has higher prio
+            currentState = states.get(mode);
+        }
     }
 
     public boolean isFrightened() {
@@ -99,6 +102,14 @@ public class Ghost extends BaseAnimated {
         return states.get(GhostMode.EATEN) == currentState;
     }
 
+    public GhostMode currentMode() {
+        return states.entrySet().stream()
+                .filter(s -> s.getValue() == currentState)
+                .map(Map.Entry::getKey)
+                .findFirst()
+                .orElse(null);
+    }
+
     public void reset() {
         currentState = states.get(GhostMode.CHASE);
         ((ChaseGhostMode) currentState).resetPosition();