Get Shadow Preview

Synthetic preview rows for one semantic-layer table ENTRY.

Keyed by entry id, not table name: several entries can share a physical table (e.g. an untagged one and an it/de-tagged one) and the preview must show the columns of the entry being edited, not whichever entry the tag-blind resolver would pick.

Generated by the deterministic shadow generator (services/evals/shadow): same definition -> same rows, bit for bit. Purely illustrative: Annie never has the customer's real data.