release: v0.1.12 — accessibility, Zen mode, scroll sync v2, shortcutHelp plugin

feat(a11y): toolbar keyboard navigation (Arrow keys, Home, End)
feat(a11y): aria-live region for screen reader announcements on mode change
feat(a11y): enhance focus-visible style (outline-offset: 2px, hide on mouse focus)

feat(core): Zen mode (editor.toggleZen() / exec('zen'))
- Toggle with Ctrl+Shift+Z shortcut concept
- Auto-hide toolbar and statusbar, mouse to top edge reveals toolbar
- Centered editor pane with max-width constraint

feat(core): heading-aware scroll sync v2
- Sync preview scroll to nearest heading before cursor position
- Falls back to proportional sync when no headings found

feat(core): Word wrap toggle (editor.toggleWordWrap() / setWordWrap(bool))

feat(plugins): shortcutHelp preset plugin
- Press '?' to open keyboard shortcuts overlay panel
- Lists built-in + user-registered shortcuts
- Click overlay or press Escape to close

style: Zen mode CSS, sr-only class, focus-visible refinement

test: 3 new tests for Zen mode, WordWrap, shortcutHelp (535 total)

chore: bump version 0.1.11 → 0.1.12 across all files

src/index.js

@@ -1,7 +1,7 @@
 /**
  * MetonaEditor - 轻量级 Markdown Editor 库
  * @module metona-editor
- * @version 0.1.11
+ * @version 0.1.12
  * @author thzxx
  * @description 现代化、零依赖、易扩展、易维护、易使用的 Markdown 编辑器库。单文件，开箱即用。
  * @license MIT
@@ -29,7 +29,7 @@ import { animationUtils } from './animations.js';
 import { DEFAULTS, ICONS, THEMES, EDIT_MODES, DEFAULT_TOOLBAR, TOOLBAR_ACTIONS } from './constants.js';
 
 // 版本信息
-const VERSION = '0.1.11';
+const VERSION = '0.1.12';
 
 /**
  * 全局默认插件队列