uv sync --extra compile fails because submodules/simple-knn is missing

[jytao6027-dotcom]

I cloned the repository exactly as described in the README:
git clone https://github.com/VisualComputingInstitute/opensplat3d.git --recursive
cd opensplat3d
uv sync

uv sync completed successfully.
However, when running:
uv sync --extra compile
I get the following error:
error: Failed to determine installation plan
Caused by:
Distribution not found at:
file:///home/.../opensplat3d/submodules/simple-knn