Fix markdown CSS not applying to comments — add lt-markdown class

comment-text divs with data-markdown were never getting the lt-markdown
class, so all scoped CSS (ul/ol/li bullets, mark, del, task items, etc.)
had no effect. Fixed in PHP template, JS comment builder, and
renderMarkdownComments().

Co-Authored-By: Claude Sonnet 4.6 <noreply@anthropic.com>

views/TicketView.php

@@ -605,7 +605,7 @@ $progressClass  = $slaBreached ? 'lt-progress--red' : ($slaPct >= 75 ? 'lt-progr
                       <?php endif ?>
                     </div>
                   </div>
-                  <div class="comment-text" id="comment-text-<?= $commentId ?>"
+                  <div class="comment-text<?= $markdownEnabled ? ' lt-markdown' : '' ?>" id="comment-text-<?= $commentId ?>"
                        <?= $markdownEnabled ? 'data-markdown' : '' ?>>
                     <?= $markdownEnabled
                         ? htmlspecialchars($comment['comment_text'])