Link the three-up boards from the venue map docs

docs/joke-shop-map.md

@@ -81,7 +81,9 @@ just as with the Hollywood day/night rows.
 
 The committed, license-cleared photo board for this block — with the provenance sidecar and the
 decisions each photo informed — is in
-[`screens/refs/joke-shop/README.md`](screens/refs/joke-shop/README.md).
+[`screens/refs/joke-shop/README.md`](screens/refs/joke-shop/README.md), and the three-up board
+(real photo | generated concept | current capture) is in
+[`screens/boards/README.md`](screens/boards/README.md).
 
 - OpenStreetMap way 428854155: <https://www.openstreetmap.org/way/428854155>
 - Wikimedia Commons photographs used for proportion and material study: