scripts: update fine-tune defaults to lr=3e-5, epochs=30

Matches the configuration that produced finetuned.pt (val ppl 2.15,
best epoch 20, early stopped at 30).

Co-Authored-By: Claude Sonnet 4.6 <noreply@anthropic.com>

scripts/train.py

@@ -55,10 +55,10 @@ TRAIN_CFG = TrainConfig(
     output=CHECKPOINT,
     init_from=INIT_FROM,
     # Small corpus (~45 train files) → ~6 batches/epoch.
-    # 50 epochs × 6 = ~300 gradient steps; patience=10 gives a 60-step window.
-    epochs=50,
+    # 30 epochs × 6 = ~180 gradient steps; patience=10 gives a 60-step window.
+    epochs=30,
     batch_size=8,
-    lr=1e-5,
+    lr=3e-5,
     warmup_steps=10,
     patience=10,
     seed=42,