feat(web): add M0 live preview editor prototype

- CodeMirror 6 editor with Obsidian/Typora-style live preview: block
  markup revealed per line, inline markup revealed per element
- Fenced code highlighting via Shiki (github-dark, JS regex engine) in a
  Web Worker, languages loaded on demand
- Lezer syntax tree to HTML renderer for share pages, checked against
  the CommonMark 0.31.2 spec (640/652; 12 known parser deviations)
- Use markdownLanguage directly to avoid bundling lang-html/css/js

web/package.json

@@ -0,0 +1,29 @@
+{
+  "name": "rawmark-web",
+  "private": true,
+  "type": "module",
+  "scripts": {
+    "dev": "vite",
+    "build": "vite build",
+    "typecheck": "tsc --noEmit",
+    "test": "vitest run"
+  },
+  "dependencies": {
+    "@codemirror/commands": "^6.11.1",
+    "@codemirror/lang-markdown": "^6.5.2",
+    "@codemirror/language": "^6.13.1",
+    "@codemirror/state": "^6.7.6",
+    "@codemirror/view": "^6.43.14",
+    "@lezer/common": "^1.5.3",
+    "@lezer/highlight": "^1.2.5",
+    "@lezer/markdown": "^1.8.0",
+    "shiki": "^4.5.0"
+  },
+  "devDependencies": {
+    "commonmark-spec": "^0.31.2",
+    "happy-dom": "^21.0.3",
+    "typescript": "^7.0.2",
+    "vite": "^8.3.4",
+    "vitest": "^5.0.5"
+  }
+}