Update root README — checkpoint-21404 logged

README.md

@@ -529,3 +529,14 @@ https://creativecommons.org/licenses/by-nc/4.0/
 **Epoch:** 0.614
 **Zone:** 🎯 Sweet Spot
 **Status:** Training ongoing — auto-uploaded via train_v12.py
+
+---
+
+### 🔵 Checkpoint — Step 21,404
+**Date:** June 29, 2026 at 18:52 IST
+**Checkpoint:** checkpoint-21404
+**Step:** 21,404 / 40,000 (53.5% complete)
+**Loss:** 0.2434
+**Epoch:** 0.625
+**Zone:** 🎯 Sweet Spot
+**Status:** Training ongoing — auto-uploaded via train_v12.py