feat(web): render canonical living hedge maze walls

docs/PLAYER_UI.md

@@ -63,6 +63,11 @@ blocked-move text. Opened-passage bits in an ordinary cell projection render as
 a permanent trampled bush gap. Effects have one restartable timer and clear on
 pause, result, reset, disconnect, and control reset. Reduced motion is static.
 
+The map draws only a bounded canonical hedge-edge layer generated from current
+received cells. It hashes each visible edge deterministically to choose the
+approved local SVG variant, so the browser neither retains unseen geometry nor
+decides topology. The layer is decorative and cannot receive input.
+
 All remaining Russian system messages use one `role=status` live message rail
 above the application top bar. One connection-loss message has highest priority
 and remains until a successful recovery; other messages deduplicate, replace