Reflected Swap Meet: the reflector chooses the trade (rev 27)

'FULL REFLECTION lets the other player decide which objects, if any,
will be swapped' — the reflector's choice now rides their counteract
(params.cardId, reflector's item first), resolved with the roles
swapped when the reflection settles; 'none' or no choice trades
nothing. The client walks the reflector through the same give-and-take
picker, with a 'swap nothing' refusal.

Also from room XRT7: the trade picker now honors each room's own rules
revision (older rooms trade only object-typed cards), so it can no
longer offer a wizardblade a rev-25 engine will quietly refuse — and a
fizzled swap finally says so in the log instead of vanishing.

Co-Authored-By: Claude Fable 5 <noreply@anthropic.com>
Claude-Session: https://claude.ai/code/session_0138A8CjeQRpvzKxuMfz1Bqc

packages/engine/test/expansion-combat.test.ts

@@ -445,3 +445,50 @@ describe("swap meet trades treasures too", () => {
     expect(state.treasures.find((t) => t.id === t2.id)!.carriedBy).toBe(attacker);
   });
 });
+
+describe("full reflection hands the swap meet choice to the reflector (rev 27)", () => {
+  function reflectedSwapRig(reflectorChoice?: string) {
+    let { state } = createGame({ playerIds: ["alice", "bob"], seed: 42, sets: ["basic", "expansion1"], deckRev: 27 });
+    state = toRound2(state);
+    const { attacker, defender } = faceOff(state);
+    const a = state.players.find((p) => p.id === attacker)!;
+    // The caster carries a treasure and offers a dagger; the reflector may
+    // instead demand the trade of their own choosing.
+    const t = state.treasures.find((t) => t.owner === attacker)!;
+    t.position = null; t.carriedBy = attacker; a.carriedTreasureId = t.id;
+    const sm = giveCard(state, attacker, "swap-meet");
+    giveCard(state, attacker, "dagger", "D", 1);
+    giveCard(state, defender, "full-reflection", "FR", 0);
+    giveCard(state, defender, "large-rock", "R", 1);
+    state = must(state, attacker, {
+      type: "cast", instanceId: sm.instanceId,
+      target: { kind: "player", playerId: defender },
+      params: { cardId: "dagger;large-rock" },
+    });
+    state = must(state, defender, {
+      type: "counteract", instanceId: "full-reflection#FR",
+      ...(reflectorChoice ? { params: { cardId: reflectorChoice } } : {}),
+    });
+    state = must(state, attacker, { type: "pass" });
+    return { state, attacker, defender, treasureId: t.id };
+  }
+
+  it("the reflector rewrites the trade: their rock for the caster's treasure", () => {
+    const { state, attacker, defender, treasureId } = reflectedSwapRig("large-rock;treasure");
+    const d = state.players.find((p) => p.id === defender)!;
+    expect(d.carriedTreasureId).toBe(treasureId);
+    expect(state.players.find((p) => p.id === attacker)!.hand.some((c) => c.cardId === "large-rock")).toBe(true);
+    expect(state.players.find((p) => p.id === attacker)!.carriedTreasureId).toBeNull();
+  });
+
+  it("the reflector may decline: 'none' trades nothing", () => {
+    const { state, attacker, defender, treasureId } = reflectedSwapRig("none");
+    expect(state.players.find((p) => p.id === attacker)!.carriedTreasureId).toBe(treasureId);
+    expect(state.players.find((p) => p.id === defender)!.hand.some((c) => c.cardId === "large-rock")).toBe(true);
+  });
+
+  it("a bare full reflection with no choice trades nothing", () => {
+    const { state, attacker } = reflectedSwapRig(undefined);
+    expect(state.players.find((p) => p.id === attacker)!.hand.some((c) => c.cardId === "dagger")).toBe(true);
+  });
+});