docs: correct the SPIDER probe path

docs: finish the GrapHist++ rename

Fix stale paths and resync the shipped modeling code

Bring the studies contents in line with what actually ships

Link the code repository; point script paths at its layout

Link the authors to their sites

Cite every source cohort, note LTS4 supervision

Make every command runnable from the repo root; fix the folder-limit and gate wording

Add authorship, remove em dashes

Rewrite DATA.md for a general audience: no branches, per-dataset reference, absorbs the study numbers

Move data docs to DATA.md and rewrite every path for the new structure

Restructure: move batch 1/30