The walkthrough guide should be updated since the App Mod extension has been updated

The App Mod extension typically doesn't have the "Run task" button anymore, so the readme guide should be updated e.g. the Asset manager tutorial

Review the README walkthrough, especially the Asset manager tutorial, and compare its instructions with the current App Mod extension behavior. Update references to the unavailable “Run task” button, then verify the guide no longer directs users to that step.

由索引模型根据 Issue 内容生成。