feat: support system-installed browsers via channel and executable path

[SantosVilanculos]

Summary

Adds two new pest()->browser() configuration options to launch system-installed browsers instead of the Playwright-bundled browsers:

// Google Chrome or Microsoft Edge via Playwright's "channel" mechanism
pest()->browser()->usingChannel('chrome');

// a Chromium-family binary via its absolute path
pest()->browser()->usingExecutablePath('/usr/bin/google-chrome');

The supported channels match Playwright's #configure-browsers docs: chrome, chrome-beta, chrome-dev, chrome-canary, msedge, msedge-beta, msedge-dev, msedge-canary.

Motivation

No downloaded Playwright browser bundles are needed — great for environments that already have Chrome/Edge installed and want to avoid npx playwright install.

Unlocks browsers on distros Playwright's installer refuses to support

Playwright's channel install scripts (bin/reinstall_chrome_stable_linux.sh, bin/reinstall_msedge_*_linux.sh) are hard-gated to Ubuntu/Debian: they source /etc/os-release and abort otherwise. On Linux Mint:

ERROR: cannot install on linuxmint distribution - only Ubuntu and Debian are supported

So a machine that already has Chrome installed still can't use the chrome channel when npx playwright install chrome is part of the bootstrap. This PR removes that whole step: the browser is launched in place, so there is no download, no distro gate, and the system installation is never touched. (On Ubuntu/Debian the Playwright installer would even apt-get remove google-chrome and reinstall the .deb — a disruptive no-op for anyone who already has Chrome.)

Verified end-to-end on Linux Mint (an unsupported distro) with the system Chrome 151: visit(...)->screenshot(...) emits real screenshots while ~/.cache/ms-playwright stays empty. Same benefit on Fedora, Arch, openSUSE, etc., and in CI images that preinstall browsers.

Implementation

• Configuration::usingChannel(string) and Configuration::usingExecutablePath(string) config methods, plus static channel/executablePath state on Playwright
• Both are forwarded as launch options in the Playwright client; the payload is URL-encoded (via http_build_query) so executable paths containing spaces or special characters round-trip correctly
• Playwright's run-server is started with --unsafe when an executablePath is set, because the server otherwise filters that launch option out (see filterLaunchOptions in playwright-core); channel is always accepted without --unsafe
• usingChannel() and usingExecutablePath() are mutually exclusive and throw an InvalidArgumentException if combined

Scope

Playwright only supports Chromium-family binaries via channel/executablePath. Branded Firefox and Safari builds are not supported because Playwright relies on its own patched builds of those browsers — so usingExecutablePath('/usr/bin/firefox') does not work. Use the bundled Firefox (inFirefox()) for Firefox tests.

Tests

• tests/Unit/Configuration/SystemBrowserConfigurationTest.php — channel/path configuration, fluent chaining, mutual-exclusion
• tests/Unit/Playwright/ClientTest.php — launch-option forwarding and connection-query encoding
• Unit + arch tests pass; Pint and PHPStan are clean

Notes

• channel is the recommended approach for Chromium-based system browsers and requires no server flags.
• executablePath requires the --unsafe server mode (added conditionally).