Add gm harness with batch chance tools for play.

Main world layer can loop on the chance tool (requests array) until settlement JSON. Driver forwards output deltas; standalone chance worker accepts batch requests. play_slots.chance gates the harness.

Co-authored-by: Cursor <cursoragent@cursor.com>

tests/gm-tools.test.ts

@@ -0,0 +1,45 @@
+import { describe, expect, it } from "vitest";
+import {
+  executeChanceBatch,
+  parseChanceBatchRequest,
+} from "../src/skills/chance-tools.js";
+import {
+  executeGmChanceTool,
+  gmChanceToolsEnabled,
+} from "../src/skills/gm-tools.js";
+
+describe("chance batch", () => {
+  it("parses requests array", () => {
+    const items = parseChanceBatchRequest({
+      requests: [
+        { id: "door", op: "roll", expression: "1d20" },
+        { id: "win", op: "compare", left: 15, right: 12 },
+      ],
+    });
+    expect(items?.map((x) => x.id)).toEqual(["door", "win"]);
+  });
+
+  it("executeGmChanceTool returns batch schema", () => {
+    const parsed = executeGmChanceTool(
+      JSON.stringify({
+        requests: [{ id: "x", op: "roll", expression: "1d6" }],
+      }),
+    );
+    expect(parsed.schema).toBe("chance.batch.v1");
+    expect(parsed.results[0]!.id).toBe("x");
+  });
+});
+
+describe("gmChanceToolsEnabled", () => {
+  it("defaults on when play_slots omitted", () => {
+    expect(gmChanceToolsEnabled(undefined)).toBe(true);
+  });
+
+  it("respects chance=false", () => {
+    expect(gmChanceToolsEnabled({ chance: false })).toBe(false);
+  });
+
+  it("enables when chance=true", () => {
+    expect(gmChanceToolsEnabled({ chance: true })).toBe(true);
+  });
+});