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/homeworld-payment-options.ts

@@ -0,0 +1,30 @@
+import type { Action, GameView } from './engine';
+import { quoteGuildPaymentRounding } from './homeworld-payment-income';
+import { reserveShipmentCost, guildShipmentCost } from './shipment-price';
+import { territory } from './board';
+
+/** Own funding and public native population only; no donor balance or hidden card access. */
+export function homeworldShipmentPaymentBlock(g: GameView, cost: number, allyPayment: number): string | null {
+  const guild = g.players.find(p => p.faction === 'guild');
+  const me = g.players.find(p => p.id === g.me)!;
+  if (!guild || g.karamaShipping?.player === g.me ||
+    !g.homeworlds?.worlds?.some(world => world.card === 'junction' && world.side === 'low')) return null;
+  const contributions = [me.id === guild.id ? 0 : cost - allyPayment,
+    me.ally === guild.id ? 0 : allyPayment];
+  return quoteGuildPaymentRounding(contributions[0] + contributions[1], contributions).unambiguous
+    ? null : 'Low Junction rounding for two odd allied contributions awaits a ruling. Choose a different payment split.';
+}
+
+export function botHomeworldShipmentPaymentAllowed(g: GameView, action: Action): boolean {
+  if (!['ship', 'guildShip'].includes(action.type)) return true;
+  if (!g.homeworlds?.worlds?.some(world => world.card === 'junction' && world.side === 'low')) return true;
+  const me = g.players.find(p => p.id === g.me)!;
+  const to = String(action.territory);
+  const amount = action.noField ? 1 : Number(action.amount);
+  const cost = action.type === 'ship'
+    ? reserveShipmentCost({ faction: me.faction, halfRate: me.faction === 'guild' ||
+      g.players.some(p => p.faction === 'guild' && p.id === me.ally) || g.karamaShipping?.player === me.id }, territory(to).type, amount)
+    : guildShipmentCost(to === 'reserves' ? 'reserves' : territory(to).type, amount);
+  const share = action.allyPayment === undefined ? Math.max(0, cost - (me.spice ?? 0)) : Number(action.allyPayment);
+  return !homeworldShipmentPaymentBlock(g, cost, share);
+}