Replace bare contenteditable divs with a full Tiptap editor (vanilla JS,
no React) inside the <folk-notes-app> web component. Adds formatting
toolbar (bold/italic/underline/strike/code, heading dropdown, lists,
blockquote, code block, link/image insert, undo/redo), slash command
menu (/ at start of empty block), syntax-highlighted code blocks via
lowlight, and task list checkboxes.
Zone-based rendering keeps the editor DOM persistent across re-renders.
Content stored as Tiptap JSON in the existing Automerge content field
with a new contentFormat discriminator. Legacy HTML notes auto-migrate
on first edit. Remote sync updates applied without cursor disruption.
Co-Authored-By: Claude Opus 4.6 <noreply@anthropic.com>
