Link the training notebook from TRAINING.md

TRAINING.md

@@ -13,6 +13,9 @@ recoverable (regime-flat AUC ≈ 0.88), waveform/channel partially recover and l
 antennas/looks, but system size and policy identity stay at chance on the payload. Training it
 reproduces that map.
 
+> **Prefer a runnable walkthrough?** [`notebooks/train_universal_eve.ipynb`](notebooks/train_universal_eve.ipynb)
+> does load → build → train → evaluate → plot the fingerprinting map end-to-end (Colab-ready).
+
 ---
 
 ## What it trains on