fix(sdk): fix loader lifecycle for consecutive offline pack imports

packages/sdk/lib/core/loader/Package.ts

@@ -964,6 +964,11 @@ export class Package {
         unpackConfig.onProgress && unpackConfig.onProgress(0);
         let totalZipNumber = 0, progress = 0;
 
+        // 每次解包前确保 loader 可用
+        if (!this.loader) {
+            this.loader = new ObjectLoader();
+        }
+
         await this.initOfflineSource(unpackConfig);
 
         if (!this.offlineZipMap && !this.offlineFlatPackages) {
@@ -998,8 +1003,7 @@ export class Package {
                         that.offlineFlatPackages = null;
                         that.offlineFlatEntryBase = null;
                         that.dataComponentMap = null;
-                        // @ts-ignore 清除loader
-                        that.loader = undefined;
+                        // 不清除 loader，避免连续导入时被上一轮异步收尾误清理
                     }
 
                     const complete = () => {
@@ -1436,7 +1440,25 @@ export class Package {
 
         const parse = (json) => {
             if (check(json.object, json)) {
-                if (!loader) return;
+                if (!loader) {
+                    // 生产环境定位: 打印关键上下文和调用栈
+                    console.error("[Package.unpackGroup] loader is undefined before parse", {
+                        uuid,
+                        rootGroupUuid,
+                        parent,
+                        callFunNum: this.callFunNum?.value,
+                        hasJson: Boolean(json),
+                        childCount: json?.object?.children?.length,
+                        currentLoader: this.loader,
+                        capturedLoader: loader,
+                        stack: new Error("[Package.unpackGroup] missing loader").stack
+                    });
+
+                    // 防止早退导致 callFunNum 无法归零，进度卡住
+                    this.callFunNum.value--;
+                    return;
+                }
+                try {
                     loader.parse(json, (group) => {
                     const bones: Bone[] = [];
                     group.getObjectsByProperty("type", "Bone", bones);
@@ -1470,6 +1492,21 @@ export class Package {
                         func.call(this, uuid, group, rootGroupUuid);
                     })
                     })
+                } catch (err) {
+                    console.error("[Package.unpackGroup] loader.parse threw", {
+                        uuid,
+                        rootGroupUuid,
+                        parent,
+                        callFunNum: this.callFunNum?.value,
+                        hasJson: Boolean(json),
+                        childCount: json?.object?.children?.length,
+                        currentLoader: this.loader,
+                        capturedLoader: loader,
+                        err,
+                        stack: err instanceof Error ? err.stack : new Error("[Package.unpackGroup] parse error").stack
+                    });
+                    throw err;
+                }
             } else {
                 const timer = setTimeout(() => {
                     clearTimeout(timer);