Add the photo-anchored variant pass with night and overcast facade frames

docs/asset-tooling.md

@@ -207,6 +207,14 @@ generation writes a `.refgen.json` sidecar next to the frame (`model`, reference
 geometry suffix) so a concept frame can always be traced back to its evidence photo. Where a
 generated frame and its reference photo disagree, the photo wins for shape.
 
+### Photo-anchored variant pass
+
+`tools/scene_concepts.py anchor --reference <photo> --context "..." --treatments day,night,weathered
+--out-dir docs/screens/concepts/<block>` generates several restaged conditions (day, night,
+weathered) of one reference photo's framing, each with its `.refgen.json` provenance sidecar, so a
+concept board stays comparable with its photo board. The reference passes the same SIDECAR licence
+gate as `--reference` on `generate`.
+
 ### Reference-board research (`refboard`)
 
 `tools/refboard.py` searches, fetches and documents Wikimedia Commons photos of a real location for