Fix README demo video URL and add direct fallback link

Author: trissim

README.md

@@ -24,10 +24,12 @@
 
 ## 🎬 Demo
 
-<video src="https://github.com/OpenHCSDev/OpenHCS/raw/main/docs/source/_static/openhcs.mp4" controls width="100%">
+<video src="https://raw.githubusercontent.com/OpenHCSDev/OpenHCS/refs/heads/main/docs/source/_static/openhcs.mp4" controls width="100%">
   Your browser does not support the video tag.
 </video>
 
+Direct video link: https://raw.githubusercontent.com/OpenHCSDev/OpenHCS/refs/heads/main/docs/source/_static/openhcs.mp4
+
 ---
 
 OpenHCS processes large microscopy datasets (100GB+) with a **compile-then-execute** architecture. Pipelines are validated across all wells *before* any processing starts, preventing failures after hours of computation. Design pipelines in the GUI, export to Python, edit as code, and re-import — switching seamlessly between visual and programmatic workflows.