Enable mixed selected-deck Discovery previews

docs/RULE_DECISIONS.md

@@ -1,5 +1,12 @@
 # Rule decision index
 
+## Mixed selected-deck Discovery alone — 29 October 2026
+
+Discovery no longer requires Nexus or independent cards when E3 is selected
+alongside Ix and/or CHOAM decks. Existing entry-order interpretations and
+unsupported interaction boundaries remain.
+[Scope](DISCOVERY_PROTOTYPE.md#mixed-selected-deck-discovery-alone--29-october-2026).
+
 ## Fresh native Homeworld No-Field — 29 October 2026
 
 Advanced Richese may provisionally place its fresh marker on its own World for