feat: Room.dark + Item.light flags and Light helper

Co-Authored-By: Claude Opus 4.8 (1M context) <noreply@anthropic.com>

Semesterprojekt/src/main/java/thb/jeanluc/adventure/game/Light.java

@@ -0,0 +1,44 @@
+package thb.jeanluc.adventure.game;
+
+import thb.jeanluc.adventure.model.Room;
+import thb.jeanluc.adventure.model.item.Item;
+import thb.jeanluc.adventure.model.item.SwitchableItem;
+
+import java.util.Collection;
+
+/** Decides whether a room is lit, given dark rooms and active light sources. */
+public final class Light {
+
+    private Light() {
+    }
+
+    /** A room is lit if it is not dark, or an active light source is carried or present. */
+    public static boolean isLit(GameContext ctx, Room room) {
+        if (!room.isDark()) {
+            return true;
+        }
+        return hasActiveLight(ctx.getPlayer().getInventory().values())
+                || hasActiveLight(room.getItems().values());
+    }
+
+    /** True if the player carries an active light source (for the HUD). */
+    public static boolean carryingLight(GameContext ctx) {
+        return hasActiveLight(ctx.getPlayer().getInventory().values());
+    }
+
+    private static boolean hasActiveLight(Collection<Item> items) {
+        for (Item it : items) {
+            if (isActiveLight(it)) {
+                return true;
+            }
+        }
+        return false;
+    }
+
+    private static boolean isActiveLight(Item it) {
+        if (!it.isLight()) {
+            return false;
+        }
+        return !(it instanceof SwitchableItem s) || s.isOn();
+    }
+}