Convert post to WP_Post object before getting terms

Use get_post() to ensure we have a proper WP_Post object
before retrieving terms. This ensures wp_get_object_terms()
can correctly access term relationships that may not be
available on raw database objects.

Co-authored-by: swissspidy <841956+swissspidy@users.noreply.github.com>

Author: Copilot

src/WP_Export_Query.php

@@ -137,6 +137,8 @@ public function nav_menu_terms() {
 	}
 
 	public function exportify_post( $post ) {
+		// Ensure we have a proper WP_Post object for term retrieval.
+		$post                             = get_post( $post );
 		$GLOBALS['wp_query']->in_the_loop = true;
 		$previous_global_post             = Utils\get_flag_value( $GLOBALS, 'post' );
 		// phpcs:ignore WordPress.WP.GlobalVariablesOverride.Prohibited -- Temporary override.