## Summary
When adding a node from the library sidebar, the node was not correctly
selected upon placing it. This was due to the canvas capturing the node
under the cursor on mouse down, however the node had not yet been
comitted to the graph at that point, and so selection was then cleared
on mouse up.
## Changes
- **What**:
- add `blockCommitPointerDown` so if the cursor is over the canvas stop
propagation to prevent LiteGraph adding the mouse handler to clear the
selection
## Review Focus
Alternative approaches considered were blocking the event in endDrag
however this then required manual cleanup of LiteGraph handlers or
overriding the `pointer.onClick` function to force selection of our
node, both felt worse than this approach.
## Screenshots (if applicable)
https://github.com/user-attachments/assets/a2eb154e-5178-4a1e-b5c7-884efd7a10c6
