feat: Add Playwright testing scaffolding infrastructure

Implements complete Playwright testing infrastructure for manual MCP testing and
as foundation for Magnitude tests.

Created:
- playwright.config.ts - Main configuration with setup project
- tests/playwright/auth.setup.ts - Authentication setup (placeholder)
- tests/playwright/fixtures.ts - Custom fixtures for authenticated/page contexts
- tests/playwright/helpers/chat.ts - Chat interaction helpers
- tests/playwright/helpers/galaxy.ts - Galaxy visualization helpers
- tests/playwright/helpers/node.ts - Node creation/management helpers
- tests/playwright/smoke.spec.ts - Basic smoke tests
- .env.test - Environment variables template

Updated:
- package.json - Added test:playwright scripts
- .gitignore - Added tests/playwright/.auth/ exclusion

Ready for manual Playwright MCP testing and Magnitude test creation.

Resolves plan: 01-playwright-scaffolding.md

🤖 Generated with [Claude Code](https://claude.com/claude-code)

Co-Authored-By: Claude <noreply@anthropic.com>

playwright.config.ts

@@ -1,40 +1,35 @@
 import { defineConfig, devices } from '@playwright/test';
 
 export default defineConfig({
-  testDir: './tests',
+  testDir: './tests/playwright',
   fullyParallel: true,
   forbidOnly: !!process.env.CI,
   retries: process.env.CI ? 2 : 0,
   workers: process.env.CI ? 1 : undefined,
   reporter: 'html',
+
   use: {
-    baseURL: 'http://localhost:3000',
+    baseURL: process.env.PLAYWRIGHT_BASE_URL || 'http://localhost:3000',
     trace: 'on-first-retry',
+    screenshot: 'only-on-failure',
   },
 
   projects: [
-    // Setup project
-    {
-      name: 'setup',
-      testMatch: /.*\.setup\.ts/,
-    },
-
-    // Chromium tests using authenticated state
+    { name: 'setup', testMatch: /.*\.setup\.ts/ },
     {
       name: 'chromium',
       use: {
         ...devices['Desktop Chrome'],
-        // Use the saved authenticated state
-        storageState: '.playwright/.auth/user.json',
+        storageState: 'tests/playwright/.auth/user.json',
       },
       dependencies: ['setup'],
     },
   ],
 
-  // Run dev server before tests
   webServer: {
     command: 'pnpm dev',
     url: 'http://localhost:3000',
     reuseExistingServer: !process.env.CI,
+    timeout: 120000,
   },
 });