Update root README — checkpoint-21000 logged

README.md

@@ -518,3 +518,14 @@ https://creativecommons.org/licenses/by-nc/4.0/
 **Epoch:** 0.585
 **Zone:** ⚠️ Overfit Risk
 **Status:** Training ongoing — auto-uploaded via train_v12.py
+
+---
+
+### 🔵 Checkpoint — Step 21,000
+**Date:** June 29, 2026 at 15:45 IST
+**Checkpoint:** checkpoint-21000
+**Step:** 21,000 / 40,000 (52.5% complete)
+**Loss:** 0.1521
+**Epoch:** 0.614
+**Zone:** 🎯 Sweet Spot
+**Status:** Training ongoing — auto-uploaded via train_v12.py