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.

.claude/scheduled_tasks.lock

@@ -0,0 +1 @@
+{"sessionId":"4a346071-a4e3-48a9-a27b-18664473b257","pid":2237975,"procStart":"181416636","acquiredAt":1778014993773}