test(perf): dedupe fixtures and reduce flaky waits

src/logging/diagnostic.test.ts

@@ -1,8 +1,10 @@
 import fs from "node:fs";
 import { afterEach, beforeEach, describe, expect, it, vi } from "vitest";
 import {
+  diagnosticSessionStates,
   getDiagnosticSessionStateCountForTest,
   getDiagnosticSessionState,
+  pruneDiagnosticSessionStates,
   resetDiagnosticSessionStateForTest,
 } from "./diagnostic-session-state.js";
 
@@ -28,9 +30,16 @@ describe("diagnostic session state pruning", () => {
   });
 
   it("caps tracked session states to a bounded max", () => {
+    const now = Date.now();
     for (let i = 0; i < 2001; i += 1) {
-      getDiagnosticSessionState({ sessionId: `session-${i}` });
+      diagnosticSessionStates.set(`session-${i}`, {
+        sessionId: `session-${i}`,
+        lastActivity: now + i,
+        state: "idle",
+        queueDepth: 1,
+      });
     }
+    pruneDiagnosticSessionStates(now + 2002, true);
 
     expect(getDiagnosticSessionStateCountForTest()).toBe(2000);
   });