Syzygy 3-4-5 tablebases (WDL, for training labels)

Syzygy 3-4-5 endgame tablebases, WDL only (145 .rtbw files, 379 MB).

Used for TRAINING LABELS: NNUE/gen_data.py --syzygy and NNUE/relabel_tb.py
replace the 5,000-node search label with tablebase truth for positions of 5
men or fewer, where the search is measurably wrong (15.7% of <=5-man result
labels and 41.6% of score signs, measured 2026-08-24).

Fetch onto a box with:
./scripts/fetch_syzygy.sh

DTZ (.rtbz) is deliberately NOT included -- training never needs it.
Source: the standard Syzygy distribution; see syzygy/fetch.sh for the URLs.