The dev chart's overlay-isolation layer (added in 9765fa2) was not
called out in helm/README.md or zddc-server-dev/Chart.yaml. Readers
comparing the two charts saw "same shape but tracks main" without
learning that the dev chart wraps the data PVC in OverlayFS so its
writes never mutate the underlying store.
Co-Authored-By: Claude Opus 4.7 (1M context) <noreply@anthropic.com>