add these things

modernized-client/src/main/java/net/runelite/api/Client.java

@@ -0,0 +1,19 @@
+package net.runelite.api;
+
+/**
+ * RuneLite Client compatibility stub.
+ * This is a simplified version for the modernized client.
+ */
+public interface Client {
+    // Basic client methods that might be called
+    default Object[] getNpcs() { return new Object[0]; }
+    default Object getLocalPlayer() { return null; }
+    default Object getInventory() { return null; }
+    default Object getEquipment() { return null; }
+    default Object getGameState() { return null; }
+    default int getTickCount() { return 0; }
+    
+    // Placeholder methods - to be implemented as needed
+    default void addChatMessage(int type, String name, String message, String sender) {}
+    default void addGameMessage(String message) {}
+}