refactor: replace chat markdown renderer

- Replace Streamdown-based chat markdown rendering with the new renderer path
- Preserve OpenChamber table, code block, and mermaid presentation
- Remove leftover Streamdown dependencies and compatibility hooks

packages/ui/package.json

@@ -52,7 +52,6 @@
     "@radix-ui/react-toggle": "^1.1.10",
     "@radix-ui/react-tooltip": "^1.2.8",
     "@remixicon/react": "^4.7.0",
-    "@streamdown/code": "^1.0.2",
     "@tanstack/react-virtual": "^3.13.18",
     "@types/react-syntax-highlighter": "^15.5.13",
     "beautiful-mermaid": "^1.1.3",
@@ -60,6 +59,7 @@
     "clsx": "^2.1.1",
     "cmdk": "^1.1.1",
     "codemirror-lang-elixir": "^4.0.0",
+    "dompurify": "^3.2.7",
     "express": "^5.1.0",
     "fuse.js": "^7.1.0",
     "ghostty-web": "^0.4.0",
@@ -67,15 +67,17 @@
     "html-to-image": "^1.11.13",
     "http-proxy-middleware": "^3.0.5",
     "motion": "^12.23.24",
+    "morphdom": "^2.7.7",
     "next-themes": "^0.4.6",
     "prismjs": "^1.30.0",
     "qrcode": "^1.5.4",
     "react": "^19.1.1",
     "react-dom": "^19.1.1",
     "react-syntax-highlighter": "^15.6.6",
+    "remend": "^1.2.1",
     "simple-git": "^3.28.0",
+    "marked": "^17.0.3",
     "sonner": "^2.0.7",
-    "streamdown": "^2.2.0",
     "strip-json-comments": "^5.0.3",
     "tailwind-merge": "^3.3.1",
     "yaml": "^2.8.1",