Fix e2e tests: add proper health check for WordPress Playground

[fellyph]

Replace the unreliable 2-second fixed wait with a polling mechanism that verifies WordPress is actually ready to accept requests:

• Poll /wp-admin/ endpoint up to 30 times (60 seconds max)
• Check for HTTP 200 or 302 response
• Log progress for debugging
• Throw error if server doesn't start in time
• Keep additional 1-second wait for plugin initialization

[github-actions]

🤖 Hi @fellyph, I've received your request, and I'm working on it now! You can track my progress in the logs for more details.

[github-actions]

📋 Review Summary

This pull request significantly improves the reliability of the e2e tests by replacing a fixed wait with a proper polling-based health check for the WordPress Playground server. The implementation is solid and includes good practices like logging and a clear timeout mechanism.

🔍 General Feedback

• The polling logic is well-implemented, correctly checking for both successful responses and redirects.
• The use of constants for maxAttempts and delayMs is appreciated for readability and maintainability.
• One minor suggestion was made to extract the hardcoded base URL into a constant to further improve maintainability.

[github-actions]

🟡 It's a good practice to avoid hardcoding URLs and ports in test files. Defining the base URL as a constant at the top of the polling logic will improve maintainability and make it easier to update if the port or host changes.

Suggested change

	const delayMs = 2000;
	let attempts = 0;
	while (attempts < maxAttempts) {
	try {
	const response = await fetch('http://127.0.0.1:9400/wp-admin/');
	if (response.ok || response.status === 302) {
	const BASE_URL = 'http://127.0.0.1:9400';
	const maxAttempts = 30;
	const delayMs = 2000;
	let attempts = 0;
	while (attempts < maxAttempts) {
	try {
	const response = await fetch(`${BASE_URL}/wp-admin/`);