fix: use controlled envDirectory in test bootstrap instead of silencing unreadable .env

Per review feedback, instead of silently skipping an unreadable .env in
Boot::loadDotEnv(), configure the test bootstrap to use a controlled
environment directory. This ensures separate-process tests don't fail
when .env becomes unreadable due to test pollution.

- Revert is_file/is_readable guard in Boot::loadDotEnv() (retain
  production error handling for unreadable .env)
- Replace null coalescing with property_exists() for envDirectory
- Set $paths->envDirectory = $paths->testsDirectory in test bootstrap

Author: gr8man

system/Boot.php

@@ -204,15 +204,10 @@ public static function preload(Paths $paths): void
      */
     protected static function loadDotEnv(Paths $paths): void
     {
-        $envDirectory = $paths->envDirectory ?? $paths->appDirectory . '/../'; // @phpstan-ignore nullCoalesce.property
-        $dotEnvPath   = rtrim($envDirectory, '\\/') . DIRECTORY_SEPARATOR . '.env';
-
-        if (! is_file($dotEnvPath) || ! is_readable($dotEnvPath)) {
-            return;
-        }
-
         require_once $paths->systemDirectory . '/Config/DotEnv.php';
-        (new DotEnv($envDirectory))->load();
+
+        $envDir = property_exists($paths, 'envDirectory') ? $paths->envDirectory : dirname($paths->appDirectory);
+        (new DotEnv($envDir))->load();
     }
 
     protected static function defineEnvironment(): void

system/Test/bootstrap.php

@@ -54,6 +54,10 @@
 require CONFIGPATH . 'Paths.php';
 $paths = new Paths();
 
+// Use a controlled environment directory for tests so that
+// separate-process tests don't fail on an unreadable .env file.
+$paths->envDirectory = $paths->testsDirectory;
+
 // Define necessary framework path constants
 defined('APPPATH')    || define('APPPATH', realpath(rtrim($paths->appDirectory, '\\/ ')) . DIRECTORY_SEPARATOR);
 defined('ROOTPATH')   || define('ROOTPATH', realpath(APPPATH . '../') . DIRECTORY_SEPARATOR);