feat: use multiple browsers for individual tests

[nexxai]

Problem

This PR was inspired by the fact that Safari's printing functionality works differently than Chrome and Firefox. I needed a way to expose certain individual tests to multiple browsers without having to run the entire test suite for each one. Previously, there was no way to run a single test against multiple browser types within the same test execution; you either have to hard-code the browser in your Pest.php configuration file, or run your entire test suite using the --browser safari syntax.

Proposed Solution

I added a new browser() method to PendingAwaitablePage that accepts an array of BrowserType enums. This allows developers to run the same assertions across multiple browsers sequentially.

Usage Examples:

Fetch /page in both Chrome and Firefox, using dark mode:

visit('/page')
    ->browser([BrowserType::CHROME, BrowserType::FIREFOX])
    ->inDarkMode()
    ->each(function ($page) {
        $page->assertSee('Content');
    });

If you want the results from each browser:

$urls = visit('/page')
    ->browser([BrowserType::CHROME, BrowserType::FIREFOX])
    ->inDarkMode()
    ->withLocale('en-US')
    ->eachResult(function ($page) {
        $page->url();
    });

Technical Details

• Added MultiBrowserPendingPage class that holds multiple PendingAwaitablePage instances
• Uses __call magic method to forward method calls (like inDarkMode(), withLocale(), etc.) to all pending pages (Note: Phpstan wasn't understanding the magic here, which is why I added the //ignore-line comment. If you are aware of a better way of handling this, please share and I'll update it)
• The each() method runs the callback on each browser sequentially, closing and reconnecting between browsers to work within Playwright's single-browser limitation
• Added closeOthers() method to Playwright class to facilitate switching between browsers
• Fixed Client::disconnect() to properly close the WebSocket connection