test(core-dsr): cover dsrRouter singleton guard proxy path

Co-Authored-By: Claude Sonnet 4.6 <noreply@anthropic.com>

packages/core-dsr/src/__tests__/dsr.router.test.ts

@@ -1,5 +1,5 @@
 import { describe, it, expect, vi } from "vitest";
-import { createDsrRouter } from "@/dsr.router";
+import { createDsrRouter, dsrRouter } from "@/dsr.router";
 import type { DsrTrpcUser } from "@/dsr.router";
 import type { DsrBinding } from "@/di/bind-production";
 import {
@@ -207,3 +207,16 @@ describe("dsrRouter.restrict", () => {
     ).rejects.toMatchObject({ code: "UNAUTHORIZED" });
   });
 });
+
+describe("dsrRouter singleton guard", () => {
+  it("throws when procedures are called without a real DsrBinding", async () => {
+    // The singleton uses a Proxy that throws on any binding property access.
+    // Procedures access binding lazily, so the Proxy error surfaces at call time.
+    const caller = dsrRouter.createCaller({
+      user: authenticatedUser,
+    } as Record<string, unknown>);
+    await expect(
+      caller.export({ subjectId: "alice", format: "json" }),
+    ).rejects.toThrow(/dsrRouter singleton/);
+  });
+});