Implement Homeworld mechanics through Caladan reinforcement checkpoint

Connect typed Homeworld custody, transport, battle, income, revival and Caladan reinforcement flows with private multiplayer recovery and controls. Preserve the optimized test workflow and keep unfinished rules modes gated. Verified with 3682 offline tests, typecheck, lint, production build and 40 HTTP tests; existing saved games remain unchanged.

game/bidding-end.ts

@@ -0,0 +1,44 @@
+import type { Game } from './engine';
+
+export type BiddingEnd = {
+  event: string;
+  turn: number;
+  owners: string[];
+  ready: string[];
+};
+
+export function biddingEndQuiet(g: Game): boolean {
+  return !!g.biddingEnd && !g.decision && !g.response && !g.truthtrance &&
+    !g.phaseOpening && !g.pendingTreacheryDiscard && !g.pendingNullentropy &&
+    !g.pendingKarama && !g.pendingRicheseGift && !g.pendingExchange &&
+    !g.pendingRichesePurchaseIncome && !g.pendingChoamMarketGhola &&
+    !g.choamMarket?.sale && !g.choamMarket?.trade;
+}
+
+/** Bidding hand counts are public. Never inspect private card identities or
+ * spice to decide whether to skip an owner's opportunity. */
+export function biddingEndPubliclyEmpty(g: Game, id: string): boolean {
+  const owner = g.players.find((p) => p.id === id)!;
+  return owner.hand.length === 0 && g.players.every((p) => p.id === id ||
+    (p.hand.length < 2 && !(p.faction === 'richese' && p.ally === id &&
+      owner.ally === p.id && p.hand.length > 0)));
+}
+
+export function biddingEndError(g: Game): string | null {
+  const end = g.biddingEnd;
+  if (!end) return null;
+  const emperor = g.players.find((p) => p.faction === 'emperor');
+  const choam = g.players.find((p) => p.faction === 'choam');
+  const owners = [emperor?.id, choam?.id].filter((id): id is string => !!id);
+  if (g.status !== 'playing' || g.phase !== 3 || end.turn !== g.turn ||
+      !g.homeworlds?.custody || !emperor ||
+      typeof end.event !== 'string' || !end.event ||
+      JSON.stringify(end.owners) !== JSON.stringify(owners) ||
+      !Array.isArray(end.ready) || new Set(end.ready).size !== end.ready.length ||
+      end.ready.some((id) => !owners.includes(id)) ||
+      !!g.auction || !!g.richeseAuction || !!g.currentAuctionSale ||
+      (choam ? g.choamMarket?.owner !== choam.id || g.choamMarket.resume !== 'phase'
+        : !!g.choamMarket))
+    return 'The saved end-of-Bidding opportunity no longer matches its owners or completed auctions.';
+  return null;
+}