ci: wire wandb logging via WANDB_API_KEY secret

When the secret is present, base_train --run=smoke-$run_number gets
logged to wandb (project=nanochat). Without the secret it falls
back to dummy / DummyWandb, so local runs stay offline.

scripts/smoke.sh

@@ -16,6 +16,13 @@ export OMP_NUM_THREADS=1
 
 mkdir -p "$CACHE_ROOT" "$NANOCHAT_BASE_DIR"
 
+# wandb: real run if WANDB_API_KEY is set, otherwise fall back to dummy (DummyWandb).
+if [ -n "${WANDB_API_KEY:-}" ]; then
+    RUN_TAG=${CI_RUN_TAG:-smoke-$(date +%Y%m%d-%H%M%S)}
+else
+    RUN_TAG=dummy
+fi
+
 if [ ! -d "$NANOCHAT_DIR" ]; then
     echo "Cloning nanochat into $NANOCHAT_DIR"
     git clone https://github.com/karpathy/nanochat.git "$NANOCHAT_DIR" \
@@ -60,6 +67,6 @@ time python -m scripts.base_train \
     --core-metric-every=-1 \
     --sample-every=25 \
     --num-iterations=50 \
-    --run=dummy
+    --run="$RUN_TAG"
 
 echo "=== smoke done ==="