Replaces the plain textarea with a WYSIWYG contenteditable editor so the formatting the parent sees while writing matches what the student sees when reading. Toolbar supports bold, italic, underline, H2/H3, bullet/numbered lists, links, and YouTube embeds. Selection is saved on editor blur and restored before each execCommand so toolbar clicks don't lose the user's selection. Co-Authored-By: Claude Sonnet 4.6 <noreply@anthropic.com>