HyzaliaPainting

- /prefabsavefluid — Opens the same prefab save UI as the vanilla Builder Tools flow, then rewrites the saved `.prefab.json` with fluids sampled from the world (water, etc.) for the current selection.
- Enrichment runs after the normal saveFromSelection pass, so behavior matches the stock save except that fluid data is always filled in, including when using an Editor_Anchor block or player anchor (paths that otherwise skip fluids).