perf(test): speed up suites and reduce fs churn

src/config/sessions.cache.test.ts

@@ -1,7 +1,7 @@
 import fs from "node:fs";
 import os from "node:os";
 import path from "node:path";
-import { afterEach, beforeEach, describe, expect, it, vi } from "vitest";
+import { afterAll, afterEach, beforeAll, beforeEach, describe, expect, it, vi } from "vitest";
 import {
   clearSessionStoreCacheForTest,
   loadSessionStore,
@@ -10,12 +10,23 @@ import {
 } from "./sessions.js";
 
 describe("Session Store Cache", () => {
+  let fixtureRoot = "";
+  let caseId = 0;
   let testDir: string;
   let storePath: string;
 
+  beforeAll(() => {
+    fixtureRoot = fs.mkdtempSync(path.join(os.tmpdir(), "session-cache-test-"));
+  });
+
+  afterAll(() => {
+    if (fixtureRoot) {
+      fs.rmSync(fixtureRoot, { recursive: true, force: true });
+    }
+  });
+
   beforeEach(() => {
-    // Create a temporary directory for test
-    testDir = path.join(os.tmpdir(), `session-cache-test-${Date.now()}`);
+    testDir = path.join(fixtureRoot, `case-${caseId++}`);
     fs.mkdirSync(testDir, { recursive: true });
     storePath = path.join(testDir, "sessions.json");
 
@@ -27,10 +38,6 @@ describe("Session Store Cache", () => {
   });
 
   afterEach(() => {
-    // Clean up test directory
-    if (fs.existsSync(testDir)) {
-      fs.rmSync(testDir, { recursive: true, force: true });
-    }
     clearSessionStoreCacheForTest();
     delete process.env.OPENCLAW_SESSION_CACHE_TTL_MS;
   });