perf: migrate chat rendering to virtua (#1651)

* refactor: migrate chat history virtualization to virtua

* refactor: render loaded chat history directly

* refactor: finish virtua migration

* perf: defer tool body rendering

* perf: queue deferred tool body mounts

* perf: quiet and defer markdown file probes

* perf: defer markdown code highlighting

* perf: stabilize markdown plugin lists

* perf: defer mermaid markdown rendering

* perf: delay markdown file reference annotation

* perf: attach markdown table listeners on demand

* perf: trim markdown render overhead

packages/ui/package.json

@@ -44,7 +44,6 @@
     "@pierre/diffs": "1.3.0-beta.4",
     "@replit/codemirror-vim": "^6.3.0",
     "@simplewebauthn/browser": "13.3.0",
-    "@tanstack/react-virtual": "^3.13.18",
     "@types/react-syntax-highlighter": "^15.5.13",
     "@xenova/transformers": "^2.17.2",
     "@zumer/snapdom": "^2.12.0",
@@ -78,6 +77,7 @@
     "sonner": "^2.0.7",
     "strip-json-comments": "^5.0.3",
     "tailwind-merge": "^3.3.1",
+    "virtua": "0.49.1",
     "yaml": "^2.8.1",
     "zod": "^4.3.6",
     "zustand": "^5.0.8"