Add guidance to avoid shadowing variable names?

[rgasper]

I find the Opus models consistently forget about shadowed variable names being an issue when I have them work on the notebooks using the marimo-pair skill. It'd be nice to have it instruct them about that to save time and tokens on writing out a notebook that's obviously broken and having to debug it!

[mscolnick]

Good idea, we can add something to references.md

[rgasper]

Similarly the agents goof on getting the setup cell right nearly 100% of the time

[manzt]

I think this should be fixed with #51 and #55