docs: replace broken RD-Agent demo links in README (#2150)

Co-authored-by: monkeyjack123 <monkeyjack123@users.noreply.github.com>
Co-authored-by: Linlang Lv (iSoftStone Information) <v-llv@microsoft.com>

Author: monkeyjack123

README.md

@@ -17,14 +17,13 @@ We are excited to announce the release of **RD-Agent**📢, a powerful tool that
 
 RD-Agent is now available on [GitHub](https://github.com/microsoft/RD-Agent), and we welcome your star🌟!
 
-To learn more, please visit our [♾️Demo page](https://rdagent.azurewebsites.net/). Here, you will find demo videos in both English and Chinese to help you better understand the scenario and usage of RD-Agent.
+To learn more, please visit the [RD-Agent repository](https://github.com/microsoft/RD-Agent). We have prepared several public demo videos for you:
 
-We have prepared several demo videos for you:
 | Scenario | Demo video (English) | Demo video (中文) |
 | --                      | ------    | ------    |
-| Quant Factor Mining | [Link](https://rdagent.azurewebsites.net/factor_loop?lang=en) | [Link](https://rdagent.azurewebsites.net/factor_loop?lang=zh) |
-| Quant Factor Mining from reports | [Link](https://rdagent.azurewebsites.net/report_factor?lang=en) | [Link](https://rdagent.azurewebsites.net/report_factor?lang=zh) |
-| Quant Model Optimization | [Link](https://rdagent.azurewebsites.net/model_loop?lang=en) | [Link](https://rdagent.azurewebsites.net/model_loop?lang=zh) |
+| Quant Factor Mining | [YouTube](https://www.youtube.com/watch?v=X4DK2QZKaKY&t=6s) | [YouTube](https://www.youtube.com/watch?v=X4DK2QZKaKY&t=6s) |
+| Quant Factor Mining from reports | [YouTube](https://www.youtube.com/watch?v=ECLTXVcSx-c) | [YouTube](https://www.youtube.com/watch?v=ECLTXVcSx-c) |
+| Quant Model Optimization | [YouTube](https://www.youtube.com/watch?v=dm0dWL49Bc0&t=104s) | [YouTube](https://www.youtube.com/watch?v=dm0dWL49Bc0&t=104s) |
 
 - 📃**Paper**: [R&D-Agent-Quant: A Multi-Agent Framework for Data-Centric Factors and Model Joint Optimization](https://arxiv.org/abs/2505.15155)
 - 👾**Code**: https://github.com/microsoft/RD-Agent/