fix: Resolve memory exhaustion with Twig-based plugins (v0.4.1)

- Add early metrics endpoint handler to intercept /metrics before full WP init
- Remove content filters during metrics collection to prevent recursion
- Skip extensibility hooks in early metrics mode
- Change template_redirect to parse_request for earlier interception

Co-Authored-By: Claude Opus 4.5 <noreply@anthropic.com>

src/Endpoint/MetricsEndpoint.php

@@ -45,7 +45,9 @@ class MetricsEndpoint {
      */
     private function init_hooks(): void {
         add_action( 'init', array( $this, 'register_endpoint' ) );
-        add_action( 'template_redirect', array( $this, 'handle_request' ) );
+        // Use parse_request instead of template_redirect to handle the request early,
+        // before themes and other plugins (like Twig-based ones) can interfere.
+        add_action( 'parse_request', array( $this, 'handle_request' ) );
     }
 
     /**
@@ -66,10 +68,13 @@ class MetricsEndpoint {
     /**
      * Handle the metrics endpoint request.
      *
+     * Called during parse_request to intercept before themes/plugins load.
+     *
+     * @param \WP $wp WordPress environment instance.
      * @return void
      */
-    public function handle_request(): void {
-        if ( ! get_query_var( 'wp_prometheus_metrics' ) ) {
+    public function handle_request( \WP $wp ): void {
+        if ( empty( $wp->query_vars['wp_prometheus_metrics'] ) ) {
             return;
         }