fix(handler): getException() returning null breaks trace building

[usernane]

Description

In production, getException() returns null for security. However, setTrace() calls getException() internally, which breaks trace building in production environments.

Current State

// In AbstractHandler.php
public function getException(): ?Throwable {
    if (!$this->security->allowRawExceptionAccess()) {
        return null;  // Returns null in production
    }
    return $this->exception;
}

private function setTrace(): void {
    $ex = $this->getException();  // Gets null in production!
    
    if ($ex === null) {
        $this->traceArr = [];  // Trace is empty in production
        return;
    }
    // ... trace building never happens
}

Implementation Details

• Use private $this->exception property directly in setTrace() instead of getException()
• Keep getException() security behavior for public access only

Acceptance Criteria

• Trace builds correctly in all environments
• Production still blocks raw exception access via public getException() method
• Add test for production trace building