style: normalize headers, overtype editor rounded corners, remove duplicate cover preview, thesis-add-header grid layout, subtitle below header with top gradient

app/templates/partials/form/form-help-block.php

@@ -4,6 +4,7 @@
  *
  * Variables consumed:
  *   string $helpContent — raw Markdown string from the DB (may be empty).
+ *   string $helpKey     — block key, used as element id.
  *
  * Outputs nothing when $helpContent is empty or whitespace-only.
  * Parsedown must already be autoloaded (it is, via bootstrap → APP_ROOT/src/).
@@ -19,7 +20,7 @@ $pd   = new Parsedown();
 $pd->setSafeMode(true);
 $html = $pd->text($helpContent);
 ?>
-<div class="form-help-block">
+<div class="student-help-block" id="help-<?= htmlspecialchars($helpKey ?? 'unknown') ?>">
     <?= $html ?>
 </div>
 <?php