Fix Playwright wait methods not executing commands

[asllanmaciel]

Summary

Consumes the Client::execute() generator in the page wait methods so their Playwright commands are actually sent.

Client::execute() is lazy because it returns a Generator; calling it and discarding the result does not execute the websocket send. waitForLoadState(), waitForFunction(), and waitForURL() were therefore silent no-ops.

This patch routes those calls through the existing processVoidResponse() helper, which consumes the generator, and adds regression coverage asserting that each wait method sends the expected Playwright message.

Fixes pestphp/pest#1892.

Test isolation follow-up

The regression tests stub the singleton Client websocket connection. A follow-up commit now clears that stub in afterEach() so the fake connection cannot leak into later tests in the same process and interfere with a real connectTo() call.

Validation

• regression coverage for waitForLoadState(), waitForFunction(), and waitForURL() is present on the current head;
• focused wait-method suite on PHP 8.4: 3 tests / 11 assertions - PASS;
• Composer quality stages reached before the browser runtime suite - Rector, style checks, profanity/type-coverage checks, and PHPStan - passed in the validation environment;
• the broader browser test run could not complete there because the Playwright browser/runtime was not installed, so no full-suite PASS is claimed;
• current GitHub Actions run for the external-fork head (Tests #1202) is action_required before jobs execute; this is an authorization gate, not a test failure;
• git diff --check is clean.

The implementation remains intentionally narrow: three existing wait methods now consume the response exactly like the other void Playwright operations, and the tests restore singleton state after each case.

AI assistance was used to help investigate, prepare, and review the patch. I reviewed the final diff and validation evidence and take responsibility for the contribution.

[Sagmedjo]

Confirming on 5.0.1: $page->page()->waitForFunction('false') returns after 0.00 s, and so does a condition that only becomes true later. The request is never sent, because the Client::execute() generator is never consumed. waitForLoadState() has the same shape. Until this is merged we wait by evaluating an async polling promise through Page::evaluate(), which consumes its generator.