feat(server): wire Discord DM pairing notifications

tests/runtime-flow.test.ts

@@ -98,8 +98,27 @@ function createMockTransport() {
   };
 }
 
+function stubDiscordFetchSuccess() {
+  vi.stubGlobal(
+    "fetch",
+    vi
+      .fn()
+      .mockResolvedValueOnce({
+        ok: true,
+        status: 200,
+        json: async () => ({ id: "dm-channel-1" })
+      })
+      .mockResolvedValueOnce({
+        ok: true,
+        status: 200,
+        json: async () => ({ id: "message-1" })
+      })
+  );
+}
+
 describe("Yonexus.Server runtime flow", () => {
   it("runs hello -> pair_request for an unpaired client", async () => {
+    stubDiscordFetchSuccess();
     const store = createMockStore();
     const transportState = createMockTransport();
     const runtime = createYonexusServerRuntime({
@@ -160,6 +179,7 @@ describe("Yonexus.Server runtime flow", () => {
   });
 
   it("completes pair_confirm -> auth_request -> heartbeat for a client", async () => {
+    stubDiscordFetchSuccess();
     let now = 1_710_000_000;
     const keyPair = await generateKeyPair();
     const store = createMockStore();