fix the paper link

README.md

@@ -74,7 +74,7 @@ Post-trained variant optimized for sparse depth completion:
 ## Links
 
 - **GitHub:** https://github.com/robbyant/lingbot-depth
-- **Paper:** [Masked Depth Modeling for Spatial Perception](https://arxiv.org/abs/2601.xxxxx)
+- **Paper:** [Masked Depth Modeling for Spatial Perception](https://arxiv.org/html/2601.17895v1)
 - **Project Page:** https://technology.robbyant.com/lingbot-depth
 
 ## Citation