revert: remove syntax highlighting feature entirely
Syntax highlighting overlay approach proved too fragile:
- pixel alignment between textarea and overlay unreliable
- transparent textarea caused invisible content bugs
- dynamic gutter width positioning added complexity
Removed:
- _highlightEditor, _doHighlight, toggleSyntaxHighlight, _positionHighlightLayer
- highlightLayer DOM element creation
- .me-highlight-layer, .mh-*, .me-textarea-highlight CSS
- syntaxHighlight config option from DEFAULTS
- highlight toggle button from demo.html
Kept: Mermaid, fileSystem, preview links, all other v0.1.14 features
thzxx
c6db68af59