chore(deps): bump @socketsecurity/lib to 5.21.0

No source changes needed — this repo doesn't import from the
`/validation` subpath that was retired in 5.21.0. All 1776
tests pass.

Author: jdalton

package.json

@@ -65,7 +65,7 @@
     "@anthropic-ai/claude-code": "2.1.92",
     "@babel/parser": "7.29.0",
     "@oxlint/migrate": "1.51.0",
-    "@socketsecurity/lib": "5.20.1",
+    "@socketsecurity/lib": "5.21.0",
     "@socketsecurity/registry": "2.0.2",
     "@types/node": "24.9.2",
     "@typescript/native-preview": "7.0.0-dev.20260415.1",