Fix docs imports

[jmarshrossney]

I failed to notice the examples are broken on gh pages because they can't import dirconf.

This is because I was running marimo export md with --sandbox, which creates a new dedicated isolated environment to run the notebook.

I thought this was smart since I could in-line each individual example's dependencies, rather than including them in pyproject.toml. However, if you do this you need to inline the local package - which means not only adding direnv to the dependencies table, but also the local path in the sources table.

It actually doesn't make sense for these notebooks to be sandboxed since they depend on some local paths (the example config and inputs). So, I'm going to revert to just building the notebooks in the project venv, with an extra dependencies table in pyproject.toml.