Keep hidden headers (header_layout 100) out of the JSON

Applied on all three render paths: stdWrap.if rule on
lib.contentElementWithHeader (before the plugin copies), the same rule in
the container element definitions, and a HiddenHeaderProcessor behind the
nb content-blocks data processor. headerLayout itself stays in the payload
so the front end can tell why the header is empty.

packages/vitec/Classes/DataProcessing/HiddenHeaderProcessor.php

@@ -0,0 +1,37 @@
+<?php
+
+declare(strict_types=1);
+
+namespace Evomedien\Vitec\DataProcessing;
+
+use TYPO3\CMS\Frontend\ContentObject\ContentObjectRenderer;
+use TYPO3\CMS\Frontend\ContentObject\DataProcessorInterface;
+
+/**
+ * header_layout 100 = "Hidden": blank the header fields in the content-blocks
+ * JSON (`data`, produced by nb-content-blocks-json in step 10 of
+ * lib.contentBlock). The layout value itself stays in the payload so the
+ * front end can still tell why the header is empty. Counterpart of the
+ * stdWrap.if rule on lib.contentElementWithHeader / the container elements
+ * (see Sets/Vitecset/setup.typoscript, decision 2026-09-04).
+ */
+final class HiddenHeaderProcessor implements DataProcessorInterface
+{
+    public function process(
+        ContentObjectRenderer $cObj,
+        array $contentObjectConfiguration,
+        array $processorConfiguration,
+        array $processedData
+    ): array {
+        $data = $processedData['data'] ?? null;
+        if (is_array($data) && (int)($data['header_layout'] ?? 0) === 100) {
+            foreach (['header', 'subheader', 'header_link'] as $key) {
+                if (isset($data[$key]) && $data[$key] !== '') {
+                    $data[$key] = '';
+                }
+            }
+            $processedData['data'] = $data;
+        }
+        return $processedData;
+    }
+}