DOC: explain WSL GUI backend setup - #32386

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For transparency: I used AI assistance to review the repository guidance and help structure the documentation wording. I reviewed the final diff, kept the scope limited to the WSL backend guide, and ran git diff --check before submitting.

This needs some work. It does not tell users how to see if WSLg is available, how to set those env variables, or how to persist this setup. I think this is not an appropriate section of docs to use AI to write (even more so than usual) - it needs someone working through it from scratch from the user's perspective to ensure all steps are covered.

I'm going to mark this as an autoclose candidate unless it's updated to show that a human wrote it and worked through the written process.

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I will add that the addition does not belong where it is. It breaks up an existing section and makes it look like the notebook, etc. troubleshooting steps are specific to WSL.

I would put it around L203.

Thanks for the guidance. I moved the WSL section next to the backend-selection guidance (around the requested location) so it no longer interrupts the troubleshooting flow. The section now links back to the backend selection and builtin-backend guidance, and the change is pushed in 61e03f3.

That makes sense. I reduced the WSL guidance to a short note covering WSLg, the DISPLAY/WAYLAND_DISPLAY check, and the headless Agg fallback. The update is pushed in 399236a.