Upgrade to react 19 (#14864)

## Summary

Upgrades to React 19. Closes
https://github.com/astral-sh/ruff/issues/14859

## Test Plan

I ran the playground locally and clicked through the different panels. I
didn't see any warning or error.

playground/package.json

@@ -19,8 +19,8 @@
     "classnames": "^2.3.2",
     "lz-string": "^1.5.0",
     "monaco-editor": "^0.52.0",
-    "react": "^18.2.0",
-    "react-dom": "^18.2.0",
+    "react": "^19.0.0",
+    "react-dom": "^19.0.0",
     "react-resizable-panels": "^2.0.0",
     "smol-toml": "^1.3.0"
   },
@@ -41,5 +41,11 @@
     "tailwindcss": "^3.2.4",
     "typescript": "^5.1.6",
     "vite": "^6.0.0"
+  },
+  "overrides": {
+    "@monaco-editor/react": {
+      "react": "$react",
+      "react-dom": "$react-dom"
+    }
   }
 }