Support unused selected decks with Nexus and Discovery

docs/RULE_DECISIONS.md

@@ -1,5 +1,12 @@
 # Rule decision index
 
+## Selected decks with Nexus or Discovery — 29 October 2026
+
+Selecting an expansion deck does not require seating its faction or enabling
+independent Ecaz cards. The new Nexus and Discovery previews retain existing
+module and unresolved interaction boundaries. [Nexus scope](NEXUS_CARD_RULES.md#selected-decks-without-independent-cards--29-october-2026);
+[Discovery scope](DISCOVERY_PROTOTYPE.md#selected-but-unused-e3-deck--29-october-2026).
+
 ## Mixed selected-deck Discovery alone — 29 October 2026
 
 Discovery no longer requires Nexus or independent cards when E3 is selected