Connect Emperor Nexus retention to original Ambassador purchases

docs/RICHESE_AMBASSADOR_IMPLEMENTATION.md

@@ -2,11 +2,37 @@
 
 7 September 2026. The Richese Ambassador now resolves its paid card acquisition for Ecaz or any of its eleven possible allied factions. The same effect can be copied through a legal Bene Gesserit Ambassador choice. Full Ecaz and expansion starts remain gated: this checkpoint verifies one effect and its supported interactions, not complete expansion games.
 
+## Emperor Nexus purchase composition — 14 October 2026
+
+Original native-Ecaz Nexus envelopes with Emperor absent now use a uniform
+beneficiary Pay/eligible Use confirmation after the committed Richese trigger.
+This selects the recommended visibly provisional outside-Bidding purchase
+composition, not a publisher-specific Nexus/Ambassador ruling. Pay continues
+the original required conditional purchase, not a new consent/decline. Only
+an actual unallied Emperor holder with three own spice, room and stock may
+retain that price. No bank payment, reimbursement or fake auction is created.
+Actual recycling/draw, native bonus and original movement/worm suffix run once.
+Original phase/resume proof also governs source-bound Homeworld arrivals;
+broader combination acceptance is not claimed.
+
+Affected13-file union111/111, types/lint/build and eight native API profiles
+pass. Actual390px Basic Use, Advanced Pay, irrelevant-card Pay and phase-one
+worm Use preserve one actual card and original entrant/arrival control with
+no overflow/errors. Native allied Harkonnen Pay gets its original bonus once;
+forming alliance still disposes held Nexus through the original rule.
+[Canonical source and policy](NEXUS_EMPEROR_RULES.md#recommended-original-ambassador-purchase--14-october-2026).
+
 ## Rules and behavior
 
 [Primary-source review](RICHESE_AMBASSADOR_RULES.md) records source precedence and composition. A fixed three-spice deck acquisition counts as a purchase for Harkonnen's extra card and Emperor's substitution for the bank. Ixian allied replacement expressly requires Bidding, so it does not apply to the implemented movement, shipment or worm entries. No artificial auction or allied shipment funding is created.
 
-Ecaz chooses whether to trigger and who receives the effect. That choice commits the token and automatically pays/draws; there is no additional beneficiary consent or result confirmation. The chosen beneficiary's current personal spice and actual hand limit apply. If payment, hand capacity or a drawable card is unavailable, the effect completes without payment or acquisition and the token remains committed. This unavailable-effect behavior is a documented interpretation of conditional resolution, rather than a specific publisher failed-cost ruling. Public eligibility and failure wording do not disclose an ally's private balance or fullness.
+Ecaz chooses whether to trigger and who receives the effect. That choice commits
+the token and normally pays/draws automatically. The supported Emperor-absent
+Nexus envelope now has the distinct confirmation above; no beneficiary veto
+is added. Current personal spice, hand limit and drawable stock still determine
+whether original Pay completes or yields no acquisition with the token spent.
+This unavailable-effect behavior is a documented interpretation, not a publisher
+failed-cost rule; public eligibility/failure does not expose private inability.
 
 The standard draw primitive recycles the discard pile when needed. The primary card and payment commit once before any income/bonus opportunity. A server-only receipt retains the original entry, beneficiary, paid card identity, fixed price and child stage. Emperor income, when applicable, precedes Harkonnen's bonus. Cancellation affects only the selected benefit; the original payment/card persist. Both child responses finish through the original Ambassador continuation, never an auction continuation. The original movement is not replayed; a pending worm queue resumes once. The five-token cohort replenishes only after all child effects finish, preserving a permanently removed BG token.