Add PHP CS Fixer and PHPStan max to CI; remove abandoned GoutteFactory

- Add friendsofphp/php-cs-fixer ^3.75 and phpstan/phpstan ^2.0 to
  require-dev; add .php-cs-fixer.dist.php (@Symfony ruleset with
  phpdoc_to_comment ignored_tags) and phpstan.neon (level max,
  treatPhpDocTypesAsCertain: false)
- Run CS Fixer and PHPStan in every CI matrix job alongside tests
- Add composer scripts: cs, cs-check, phpstan
- Add .php-cs-fixer.cache to .gitignore
- Fix all PHPStan max violations across src/: add return/param types,
  narrow mixed config values with is_string()/is_array() guards,
  use TaggedNodeInterface for scenario tag access in SessionsListener
- Remove GoutteFactory and its spec — the goutte driver and its
  underlying client library are abandoned

Co-Authored-By: Claude Sonnet 4.6 (1M context) <noreply@anthropic.com>

src/Behat/MinkExtension/ServiceContainer/Driver/DriverFactory.php

@@ -18,35 +18,14 @@ use Symfony\Component\DependencyInjection\Definition;
  */
 interface DriverFactory
 {
-    /**
-     * Gets the name of the driver being configured.
-     *
-     * This will be the key of the configuration for the driver.
-     *
-     * @return string
-     */
-    public function getDriverName();
+    public function getDriverName(): string;
+
+    public function supportsJavascript(): bool;
+
+    public function configure(ArrayNodeDefinition $builder): void;
 
     /**
-     * Defines whether a session using this driver is eligible as default javascript session
-     *
-     * @return boolean
+     * @param array<string, mixed> $config
      */
-    public function supportsJavascript();
-
-    /**
-     * Setups configuration for the driver factory.
-     *
-     * @param ArrayNodeDefinition $builder
-     */
-    public function configure(ArrayNodeDefinition $builder);
-
-    /**
-     * Builds the service definition for the driver.
-     *
-     * @param array $config
-     *
-     * @return Definition
-     */
-    public function buildDriver(array $config);
+    public function buildDriver(array $config): Definition;
 }