ADD joins two number cards on movement, as printed

"You may add two NUMBER cards together for any single action" —
movement included. The engine accepts a second movement number when an
ADD accompanies it (once per turn); the client spends your Add
automatically and says so on the button. 120 tests passing.

Co-Authored-By: Claude Fable 5 <noreply@anthropic.com>

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

@@ -246,3 +246,23 @@ describe("thumb of god (divine meteor)", () => {
     expect(allObjects.some((c) => c.cardId === "dagger")).toBe(true);
   });
 });
+
+describe("add for movement", () => {
+  it("an ADD permits a second number card on movement, once", () => {
+    let { state } = newGame();
+    const me = activePlayer(state).id;
+    giveCard(state, me, "number-3", "N1", 0);
+    giveCard(state, me, "number-2", "N2", 1);
+    giveCard(state, me, "add", "A", 2);
+    giveCard(state, me, "number-4", "N3", 3);
+    state = must(state, me, { type: "playNumberForMovement", instanceId: "number-3#N1" });
+    expect(state.turn.movementAllowance).toBe(6);
+    // Second without ADD: refused.
+    expect(applyCommand(state, me, { type: "playNumberForMovement", instanceId: "number-2#N2" }).ok).toBe(false);
+    // With ADD: allowed.
+    state = must(state, me, { type: "playNumberForMovement", instanceId: "number-2#N2", addInstanceId: "add#A" });
+    expect(state.turn.movementAllowance).toBe(8);
+    // A third is refused even with another add wished for.
+    expect(applyCommand(state, me, { type: "playNumberForMovement", instanceId: "number-4#N3" }).ok).toBe(false);
+  });
+});