Snippet single: Make sidebar sticky

Ideally, we want the box with the actions and save buttons to be sticky, so its always visible when there is a long scroll. 

[Related Discord Comment.](https://discord.com/channels/1003969099057070120/1003969153432039454/1422542027882758164)

<img width="346" height="535" alt="Image" src="https://github.com/user-attachments/assets/d8d66ee6-6844-4b8a-88ee-d65c79521bd8" />

cc @sheabunge @imantsk 