feat(lab): enable ReferencedDataGate feature flag on cell overlay

Activates the scheduling-gate + Instance-level Ready=False/SourceNotFound
contract for the lab (datum-us-central-1-lab). The flag is set in the
cell overlay's ConfigMap patch so it only affects deployments using the
cell OCI bundle (lab); management-plane and dev overlays are unaffected.

Co-Authored-By: Claude Sonnet 4.6 <noreply@anthropic.com>
(cherry picked from commit 2cf963f)

Author: scotwells

config/overlays/cell/disable_webhook_patch.yaml

@@ -10,3 +10,5 @@ data:
       bindAddress: "0"
     discovery:
       quotaKubeconfigPath: /etc/quota-credentials/kubeconfig
+    featureFlags:
+      enableReferencedDataGate: true