Fix counter, add input binding, syntax highlighting, dark mode

- Fix increment button: custom action handler instead of no-op setState
- Toggle visibility on Show/Hide Details button via $cond
- Input uses $bindState + useBoundProp for two-way binding
- Add shiki syntax highlighting (catppuccin-latte/mocha dual theme)
- Dark mode via prefers-color-scheme with CSS variables
- Layout: Live UI left, JSX Source + JSON Output stacked right

Co-authored-by: Ona <no-reply@ona.com>

example/package.json

@@ -8,11 +8,12 @@
     "start": "NODE_ENV=production bun src/server.ts"
   },
   "dependencies": {
-    "jrx": "file:..",
     "@json-render/core": "0.10.0",
     "@json-render/react": "0.10.0",
+    "jrx": "file:..",
     "react": "19.2.4",
-    "react-dom": "19.2.4"
+    "react-dom": "19.2.4",
+    "shiki": "^4.0.0"
   },
   "devDependencies": {
     "@types/bun": "latest",