Adjusted pseudo r squared mcfadden

I suggest including the adjusted pseudo r squared mcfadden in the statistics reported of export_summs. Currently, pseudo r squared mcfadden is reported if pseudo.r.squared.mcfadden is called in statistics

Start by locating export_summs and its handling of pseudo.r.squared.mcfadden. Check how statistics are selected and how adjusted McFadden pseudo-R² should be represented alongside the current metric. Done means export_summs reports the adjusted value consistently with the existing pseudo-R² behavior, with regression coverage if corresponding tests exist.

Written by the indexing model from the issue text.