Add evo_megamenu_json extension and seed the megamenu

- new project-neutral extension evo_megamenu_json (Evomedien): a Megamenu
  plugin holding entries, columns, items, teaser cards and a featured slot
  as nested records; presentation settings travel with the payload so the
  front end reads behaviour instead of hard-coding it; published as
  page.10.fields.megaMenu, driven by the site settings megamenu.contentUid
  and megamenu.storagePid
- vitec:seed-megamenu fills one element from the live structure: 5 entries,
  26 columns, 95 items, 4 story cards; items without a page yet are flagged
  pending so the front end falls back to the column link
- vitec:debug-sets prints the resolved site set order
- read-only diagnostics: check_megamenu_schema.php, check_typoscript_templates.php
- docs: schema updates run via extension:setup (database:updateschema no
  longer exists in v14), and a JSON Accept header activates headless-mixed,
  which strips every set-added page field

packages/vitec/Classes/Command/DebugSetsCommand.php

@@ -0,0 +1,84 @@
+<?php
+
+declare(strict_types=1);
+
+namespace Evomedien\Vitec\Command;
+
+use Symfony\Component\Console\Attribute\AsCommand;
+use Symfony\Component\Console\Command\Command;
+use Symfony\Component\Console\Input\InputInterface;
+use Symfony\Component\Console\Input\InputOption;
+use Symfony\Component\Console\Output\OutputInterface;
+use TYPO3\CMS\Core\Site\SiteFinder;
+use TYPO3\CMS\Core\Utility\GeneralUtility;
+
+/**
+ * Diagnostic: prints the site sets in the order TYPO3 actually resolves them.
+ *
+ * Set order decides who wins: friendsoftypo3/headless resets the whole `page`
+ * object (`page < lib.headlessPage`), so every set that adds page-level
+ * fields has to load AFTER it. When headless ends up last, those fields
+ * vanish without any error - which is exactly the failure this command was
+ * written for (2026-09-11).
+ *
+ *   vendor/bin/typo3 vitec:debug-sets
+ */
+#[AsCommand(
+    name: 'vitec:debug-sets',
+    description: 'Print the resolved site set order (diagnoses page-level TypoScript being reset)'
+)]
+final class DebugSetsCommand extends Command
+{
+    protected function configure(): void
+    {
+        $this->addOption('site', null, InputOption::VALUE_REQUIRED, 'Site identifier', 'vitec');
+    }
+
+    protected function execute(InputInterface $input, OutputInterface $output): int
+    {
+        $identifier = (string)$input->getOption('site');
+        $site = GeneralUtility::makeInstance(SiteFinder::class)->getSiteByIdentifier($identifier);
+
+        if (!method_exists($site, 'getSets')) {
+            $output->writeln('<error>This TYPO3 version does not expose Site::getSets().</error>');
+            return Command::FAILURE;
+        }
+
+        $sets = $site->getSets();
+        $output->writeln(sprintf('Site "%s": %d sets, in load order', $identifier, count($sets)));
+
+        $position = 0;
+        $headlessAt = null;
+        $vitecAt = null;
+        foreach ($sets as $set) {
+            $position++;
+            $name = is_object($set) && property_exists($set, 'name') ? (string)$set->name : (string)$set;
+            if ($name === 'friendsoftypo3/headless') {
+                $headlessAt = $position;
+            }
+            if ($name === 'evomedien/vitecset') {
+                $vitecAt = $position;
+            }
+            $mark = in_array($name, ['friendsoftypo3/headless', 'evomedien/vitecset'], true) ? '  <-- ' : '      ';
+            $output->writeln(sprintf('%2d.%s%s', $position, $mark, $name));
+        }
+
+        $output->writeln('');
+        if ($headlessAt === null || $vitecAt === null) {
+            $output->writeln('<comment>headless or vitecset is not in the resolved list at all.</comment>');
+            return Command::SUCCESS;
+        }
+        if ($headlessAt > $vitecAt) {
+            $output->writeln(sprintf(
+                '<error>PROBLEM: headless loads at %d, AFTER vitecset at %d - it resets `page` and drops the page-level fields.</error>',
+                $headlessAt, $vitecAt
+            ));
+        } else {
+            $output->writeln(sprintf(
+                '<info>Order is fine: headless at %d, vitecset at %d.</info>',
+                $headlessAt, $vitecAt
+            ));
+        }
+        return Command::SUCCESS;
+    }
+}