feat: multi-package loading with base framework support

- Add RuntimeOptions.basePackages for loading framework packages before game package
- Add ScriptEngine.loadPackages() for multi-package module merging
- LuaDardoScriptEngine merges modules from all packages, game overrides framework
- PackageActivationController loads base packages first, then game package
- GamePackageManifest parses optional 'base' field
- Update docs: README, quick-start, lua-package-format, architecture
- Update all test mocks with loadPackages() implementation

lib/runtime/packages/game_package_activation_controller.dart

@@ -1,4 +1,5 @@
 import '../audio/runtime_audio_manager.dart';
+import '../game/runtime_options.dart';
 import '../models/game_diff.dart';
 import '../resources/game_resource_manager.dart';
 import '../scripting/runtime_script_services.dart';
@@ -15,6 +16,7 @@ class PackageActivationController {
     required this.scriptEngine,
     this.audio,
     this.runtimeApiVersion = 1,
+    this.runtimeOptions = const RuntimeOptions(),
     this.store = const StablePackageStore(),
     this.assetFallback = const AssetGamePackageRepository(),
     this.resourceManagerFactory,
@@ -28,6 +30,7 @@ class PackageActivationController {
   final ScriptEngine scriptEngine;
   final RuntimeAudioManager? audio;
   final int runtimeApiVersion;
+  final RuntimeOptions runtimeOptions;
   final StablePackageStore store;
   final GamePackageRepository assetFallback;
   final GameResourceManager Function()? resourceManagerFactory;
@@ -143,12 +146,34 @@ class PackageActivationController {
     try {
       await verifier.verify(candidate);
       _ensureContinue(shouldContinue);
+
+      // 加载 base packages（框架包），按 runtimeOptions.basePackages 顺序。
+      final basePackages = <GamePackage>[];
+      for (final baseId in runtimeOptions.basePackages) {
+        final baseCandidates = await _candidatePackages(
+          baseId,
+          shouldContinue,
+        );
+        for (final baseCandidate in baseCandidates) {
+          try {
+            await verifier.verify(baseCandidate);
+            basePackages.add(baseCandidate);
+            break;
+          } catch (_) {
+            // Try next candidate.
+          }
+        }
+      }
+
       await preparedResources.mount(candidate);
       _ensureContinue(shouldContinue);
       await preparedAudio?.mount(candidate);
       _ensureContinue(shouldContinue);
-      await preparedScriptEngine.loadPackage(
-        candidate,
+
+      // 合并 base + game 包，传给脚本引擎。
+      final allPackages = [...basePackages, candidate];
+      await preparedScriptEngine.loadPackages(
+        allPackages,
         services: scriptServices,
       );
       _ensureContinue(shouldContinue);