Rev 19: breaching the rim opens a new warp across the maze

Destroying a wall on the board's outer edge used to leave a one-sided
hole into nothing. The table's physics prevail: the outer rim wraps,
so the breach goes clean through — the opposite perimeter wall in the
same row or column crumbles too (collapse damage and all), and a new
warp pair opens between the two edges, shimmering at both mouths.
Rev-gated: stored games hold one-sided breaches and replay so. Sector
moves recompute the wraparounds and forget improvised openings, as
the maze's own reshaping always has.

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

packages/engine/test/board.test.ts

@@ -9,6 +9,7 @@ import {
   type SectorPlacement,
 } from "../src/board";
 import { buildDeck } from "../src/cards";
+import { edgeKey, type Side } from "../src/board";
 import { activePlayer, applyCommand, boardView, createGame, gameLos } from "../src/game";
 import { createRng } from "../src/rng";
 import { setupBoard } from "../src/setups";
@@ -279,3 +280,38 @@ describe("bricking over a warp mouth", () => {
     expect(stepTarget(boardView(r2.state), w.from.cell, w.from.side).kind).toBe("warp");
   });
 });
+
+describe("breaching the rim (rules rev 19)", () => {
+  it("destroying a perimeter wall opens both sides as a new warp", () => {
+    let { state } = createGame({ playerIds: ["a", "b"], seed: 42, sets: ["basic"], deckRev: 19 });
+    for (let i = 0; i < 2; i++) {
+      const r = applyCommand(state, activePlayer(state).id, { type: "endTurn", draw: 0 });
+      if (!r.ok) throw new Error(r.error);
+      state = r.state;
+    }
+    // Find a rim wall with a wrap counterpart that is NOT already an opening.
+    const view = boardView(state);
+    for (const key of Object.keys(view.cells)) {
+      const [x, y] = key.split(",").map(Number) as [number, number];
+      for (const side of ["N", "E", "S", "W"] as Side[]) {
+        const n = { x: x + (side === "E" ? 1 : side === "W" ? -1 : 0), y: y + (side === "S" ? 1 : side === "N" ? -1 : 0) };
+        if (view.cells[`${n.x},${n.y}`]) continue;
+        if ((view.edges[edgeKey({ x, y }, side)] ?? "open") !== "wall") continue;
+        const caster = activePlayer(state);
+        caster.position = { x, y };
+        caster.hand[0] = { instanceId: "dw#1", cardId: "destroy-wall" };
+        const warpsBefore = state.board.warps.length;
+        const r = applyCommand(state, caster.id, {
+          type: "cast", instanceId: "dw#1", target: { kind: "edge", cell: { x, y }, side },
+        });
+        if (!r.ok) throw new Error(r.error);
+        if (r.state.board.warps.length === warpsBefore) continue; // no counterpart in this row
+        expect(r.state.board.warps.length).toBe(warpsBefore + 2);
+        const w = r.state.board.warps[warpsBefore]!;
+        expect(stepTarget(boardView(r.state), w.from.cell, w.from.side).kind).toBe("warp");
+        return;
+      }
+    }
+    throw new Error("setup: no breachable rim wall found");
+  });
+});