5a73d7d3e5
Rebuild the memo editor as a single CodeMirror 6 "decorated source" editor. The document is the raw markdown, stored verbatim and styled in place (markers stay visible), so the editor never serializes a tree back to markdown — removing the round-trip fidelity bug class (inline images, setext headings, ordered-list indentation, HTML entities) that the old editor needed per-case patches for. - MemoEditor/Editor: CodeMirror 6 + lang-markdown (GFM). Tokens, heading lines, #tag/@mention, and the autocomplete popover are styled in plain CSS (Editor/editor.css) with theme tokens, not a CSS-in-JS theme. - Tab/Shift-Tab nest/outdent list items (marker-aware, ordered items renumbered so nesting is CommonMark-valid); Escape blurs; #tag autocomplete sourced from useTagCounts. - Focus-mode toolbar reimplemented as markdown-text ops; active state read from the Lezer tree via the backend-agnostic formatting/commands catalog. - Remove the old serialize-back-to-markdown editor (its Editor dir, PlainEditor, the editor-mode system) and its now-unused dependencies (marked, textarea-caret, and the rich-text editor packages). - Consolidate toolbar components under Toolbar/. Read-only MemoContent rendering is unchanged.