feat: add test entry point that discovers and executes JSON tests

Created e2e/tests.ts:
- Auto-discovers all packages/*/playwright/tests.json files
- Registers them as Playwright tests at runtime
- Uses json-runner to interpret JSON test definitions
- Loads:
  - packages/system_critical_flows/playwright/tests.json (24 tests)
  - packages/ui_home/playwright/tests.json (existing tests)
  - Any other packages with playwright/tests.json

Execution:
  npm run test:e2e

This enables the complete JSON test interpreter pattern:
- Tests live in packages (not e2e/)
- JSON definitions in playwright/tests.json
- Auto-discovered at runtime
- Executed by Playwright

Co-Authored-By: Claude Haiku 4.5 <noreply@anthropic.com>

e2e/tests.ts

@@ -0,0 +1,16 @@
+/**
+ * Playwright Tests - Auto-discover and execute JSON test definitions
+ *
+ * This file loads all JSON test definitions from packages/*/playwright/tests.json
+ * and registers them as Playwright tests at runtime.
+ *
+ * Usage: npm run test:e2e
+ */
+
+import { test } from '@playwright/test'
+import { loadAllPackageTests } from './json-runner/playwright-json-runner'
+import { resolve } from 'path'
+
+// Discover and register all JSON tests from packages
+const packagesDir = resolve(__dirname, '../packages')
+void loadAllPackageTests(packagesDir, test)