test(muse): exercise child history replay without a live setup turn

Seed a historical child after closing an empty session so the replay
regression reaches resume even when live subagent projection is broken.
Both paths now fail independently with the reported negotiation error.

Co-authored-by: George <90179633+georgepullen@users.noreply.github.com>

packages/server/src/server/plugins/runtime.posix.test.ts

@@ -445,17 +445,23 @@ register(${JSON.stringify(guardUrl)});`;
     });
     try {
       const first = await client.createSession({ provider: "muse", cwd: process.cwd() });
-      const firstEvents: AgentStreamEvent[] = [];
-      first.subscribe((event) => firstEvents.push(event));
-      await first.startTurn("dispatch a subagent", { clientMessageId: "muse-history" });
-      await expectTurnCompleted(firstEvents);
       const persistence = first.describePersistence();
       expect(persistence).not.toBeNull();
       await first.close();
 
-      // Resuming replays the recorded native history, which contains the
-      // subagent item: the child must be projected again, not fail the
-      // connection the way a timeline fetch did on 0.11.2.
+      // Seed old history without running a live subagent first, so this test
+      // reaches resume even when live child projection is broken.
+      await writeFile(
+        path.join(historyDirectory, "native-history.ndjson"),
+        JSON.stringify({
+          itemId: "historical-subagent",
+          revision: 1,
+          kind: "toolCall",
+          status: "completed",
+          tool: "subagent_spawn",
+          childSessionId: "fixture-child",
+        }) + "\n",
+      );
       const resumed = await client.resumeSession(persistence!, { cwd: process.cwd() });
       const resumedEvents: AgentStreamEvent[] = [];
       resumed.subscribe((event) => resumedEvents.push(event));