fix(server): drop stale snapshot mutation ownership assertions

Session.unarchiveAgentState(id) and the direct agentManager.unarchiveSnapshotByHandle
delegation were removed when main's 86bb5cc8 + a11c246b refactors moved unarchive
through the shared mcp-shared helper. Remove the now-dead test assertions so the
suite reflects the real ownership boundary.

packages/server/src/server/snapshot-mutation-ownership.test.ts

@@ -65,8 +65,6 @@ describe("snapshot mutation ownership boundary", () => {
         updatedAt: archivedAt,
       };
     });
-    const unarchiveSnapshot = vi.fn(async () => true);
-    const unarchiveSnapshotByHandle = vi.fn(async () => undefined);
     const updateAgentMetadata = vi.fn(async () => undefined);
     const directStorageWrite = vi.fn(async () => {
       throw new Error("Session should not write snapshots directly");
@@ -93,8 +91,6 @@ describe("snapshot mutation ownership boundary", () => {
         listAgents: () => [],
         getAgent: () => null,
         archiveSnapshot,
-        unarchiveSnapshot,
-        unarchiveSnapshotByHandle,
         updateAgentMetadata,
       } as any,
       agentStorage: {
@@ -133,13 +129,6 @@ describe("snapshot mutation ownership boundary", () => {
     expect(archiveSnapshot).toHaveBeenCalledTimes(1);
     expect(archiveResult.archivedAt).toBeTruthy();
 
-    await session.unarchiveAgentState("agent-1");
-    expect(unarchiveSnapshot).toHaveBeenCalledWith("agent-1");
-
-    const handle = { provider: "codex", sessionId: "session-1" };
-    await session.unarchiveAgentByHandle(handle);
-    expect(unarchiveSnapshotByHandle).toHaveBeenCalledWith(handle);
-
     await session.handleUpdateAgentRequest(
       "agent-1",
       "Renamed agent",