Add platform adapter contract

src/main/java/com/livingworld/platform/PlatformAdapter.java

@@ -0,0 +1,25 @@
+package com.livingworld.platform;
+
+import java.nio.file.Path;
+
+/**
+ * Loader boundary used by the Living World bootstrap.
+ */
+public interface PlatformAdapter {
+
+    String getPlatformName();
+
+    String getMinecraftVersion();
+
+    String getLoaderVersion();
+
+    boolean isDedicatedServer();
+
+    Path getWorldSaveDirectory();
+
+    void registerCommands();
+
+    void registerServerTickHook();
+
+    void registerPlayerEventHooks();
+}