feat: render mermaid fences as diagrams with click-to-zoom (#7)

* feat: render mermaid fences as diagrams in chat markdown

* feat: add zoom for mermaid diagrams - opened in native size in separate window

package.json

@@ -60,6 +60,7 @@
     "class-variance-authority": "^0.7.1",
     "clsx": "^1.2.1",
     "lucide-react": "^0.539.0",
+    "mermaid": "^11.15.0",
     "next": "^16.2.5",
     "nuqs": "^2.8.8",
     "react": "19.1.0",
@@ -67,6 +68,8 @@
     "react-markdown": "^9.0.1",
     "react-resizable-panels": "^3.0.6",
     "react-syntax-highlighter": "^15.6.1",
+    "rehype-raw": "^7.0.0",
+    "rehype-sanitize": "^6.0.0",
     "remark-gfm": "^4.0.0",
     "sonner": "^2.0.7",
     "swr": "^2.4.1",