fix(test): P1-02 browser chat — add SaaS auth fixture for non-Tauri mode

Root cause: Playwright external Chromium is not a Tauri runtime, so
isTauriRuntime() returns false. The app needs SaaS session to route
chat through relay, but tests never logged in.

Fix: Auto-detect non-Tauri mode and pre-login via SaaS API, injecting
session into localStorage before tests run.

desktop/tests/e2e/specs/smoke_chat.spec.ts

@@ -6,12 +6,53 @@
  *
  * 前提条件:
  * - Desktop App 运行在 http://localhost:1420 (pnpm tauri dev)
+ * - SaaS Server 运行在 http://localhost:8080 (浏览器模式需要)
  * - 后端服务可用 (SaaS 或 Kernel)
  *
  * 运行: cd desktop && npx playwright test smoke_chat
  */
 
-import { test, expect, type Page } from '@playwright/test';
+import { test as base, expect, type Page } from '@playwright/test';
+
+const SaaS_BASE = 'http://localhost:8080/api/v1';
+const ADMIN_USER = 'admin';
+const ADMIN_PASS = 'admin123';
+
+// Extend test with SaaS login fixture for browser-mode tests
+const test = base.extend<{
+  saasAuthenticated: void;
+}>({
+  saasAuthenticated: [async ({ page }, use) => {
+    // Check if running in Tauri — if so, no SaaS login needed
+    const isTauri = await page.evaluate(() => !!(window as any).__TAURI_INTERNALS__).catch(() => false);
+
+    if (!isTauri) {
+      // Browser mode: need SaaS session before chat can work
+      // Login via SaaS API and store session in localStorage
+      try {
+        const loginRes = await page.request.post(`${SaaS_BASE}/auth/login`, {
+          data: { username: ADMIN_USER, password: ADMIN_PASS },
+        });
+        if (loginRes.ok()) {
+          const loginJson = await loginRes.json();
+          // Inject SaaS session into localStorage so the app can connect
+          await page.evaluate((session) => {
+            localStorage.setItem('zclaw-saas-session', JSON.stringify({
+              saasUrl: 'http://localhost:8080',
+              token: session.token,
+              account: session.account,
+            }));
+          }, loginJson);
+        } else {
+          console.log(`SaaS login failed (${loginRes.status()}), browser chat may not work`);
+        }
+      } catch (e) {
+        console.log('SaaS server not reachable, browser chat will not work:', (e as Error).message);
+      }
+    }
+    await use();
+  }, { auto: true }],
+});
 
 test.setTimeout(120000);