Move legacy and new code
>>> [!note] Migrated issue
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<!-- Migrated from issue #3556790. -->
Reported by: [saschaeggi](https://www.drupal.org/user/1999056)
Related to !718
>>>
<h3 id="summary-problem-motivation">Problem/Motivation</h3>
<p>Move "new" Code based on Claro into root directory from <code>merge</code> and move Gin's overrides into an <code>migration</code> folder.</p>
<ul>
<li><code>merge</code> → <code>root</code></li>
<li><code>dist</code> → <code>migration</code></li>
</ul>
issue