chore: remove unused esbuild-polyfill and suppress Rolldown inject warning

Remove @esbuild-plugins/node-globals-polyfill (redundant since Vite 8
rolldownOptions.define handles globalThis). Add rolldownOptions.checks
to suppress PREFER_BUILTIN_FEATURE until Vite exposes output in rolldownOptions.

Co-Authored-By: Claude Sonnet 4.6 <noreply@anthropic.com>

package.json

@@ -130,7 +130,6 @@
   },
   "devDependencies": {
     "@element-hq/element-call-embedded": "0.19.4",
-    "@esbuild-plugins/node-globals-polyfill": "0.2.3",
     "@rollup/plugin-inject": "5.0.5",
     "@rollup/plugin-wasm": "6.2.2",
     "@semantic-release/exec": "7.1.0",