labs/aicharts: fix model spelling drift, show the model's answer on failure (#37)

First live run: Workers AI answered specs the validator refused (agg spelling).
normalizeSpec fixes case and common aliases only; on a 422 the response
carries model_said (shown, never run). Smoke now fails on a bad spec.


Claude-Session: https://claude.ai/code/session_01VDkN7ukK1kXkqov8FaZxva

Co-authored-by: Claude <noreply@anthropic.com>

.github/workflows/labs-aicharts.yml

@@ -26,6 +26,7 @@ jobs:
           TIME_VENTURE_DOMAIN: ${{ vars.TIME_VENTURE_DOMAIN }}
       - name: smoke
         run: |
+          set -o pipefail
           u="${{ steps.deploy.outputs.url }}"
           for i in $(seq 1 18); do curl -fsS "${u}api/health" && break; sleep 10; done
           curl -fsS "${u}api/schema?dataset=orders" | python3 -c 'import json,sys; d=json.load(sys.stdin); assert len(d["sample"])==5, d; print("schema ok")'