feat: render actual elements in markdown cheatsheet instead of labels

Replace text labels (h1, bold, italic) with rendered HTML in the Rendu column:
headings, strong, em, del, code, links, blockquote, lists, hr, sup, small

TODO.md

@@ -1,9 +1,15 @@
 # TODO
 
-- [x] Create CharteController.php (public-facing controller)
-- [x] Add /charte routes to Dispatcher.php
-- [x] Create public/charte.php template
-- [x] Add 'charte' to allowed slugs in contenus.php
-- [x] Add 'charte' to allowed slugs in contenus-edit.php
-- [x] Add 'charte' to allowed slugs in page.php action
-- [x] Add Charte link to public header navigation (header.php)
+## HTMX v2 Migration
+
+Reference: `docs/autosave-system.md` → "HTMX v2 Migration Plan" section.
+
+- [x] `contenus-edit.php` (pages): Add `hx-*` attrs, add `overtype:change` dispatch in OverType `onChange`
+- [x] `contenus-edit.php` (form_help): Add `hx-*` attrs, add `overtype:change` dispatch in OverType `onChange`
+- [x] `apropos-groups-form.php` (contacts): Add `hx-*` attrs only
+- [x] `contenus-edit.php` (sidebar_links): Add `hx-*` attrs only
+- [x] Add `handleAutosaveResponse()` shared handler + `htmx:beforeRequest` loading state
+- [x] Delete `autosave.js`
+- [x] Fix backend `$isAjax` detection: also recognize `HX-Request` header (page.php, apropos.php, form-help.php)
+- [x] Form-help inline editors: add OverType toolbar + HTMX auto-save + remove save buttons
+- [x] Markdown cheatsheet modal: reusable dialog on all OverType editors