fix: suppress matrix-js-sdk push rule warnings for unimplemented MSCs

Synapse does not yet ship MSC3786/MSC3914 as server-default push rules.
matrix-js-sdk patches them client-side every login and warns. Filter these
at console.warn level -- functionality is unaffected.

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

src/index.tsx

@@ -78,6 +78,18 @@ window.addEventListener('vite:preloadError', () => {
 // Clear the reload flag after a successful load so future deploys can still trigger a reload
 window.addEventListener('load', () => sessionStorage.removeItem('chunk-reload-attempted'));
 
+
+// Synapse does not yet ship MSC3786/MSC3914 as server-default push rules.
+// matrix-js-sdk patches them client-side on every login and logs a warn for each.
+// Suppress the noise until Synapse implements these MSCs upstream.
+{
+  const _warn = console.warn.bind(console);
+  console.warn = (...args: unknown[]) => {
+    if (typeof args[0] === 'string' && args[0].startsWith('Adding default global ')) return;
+    _warn(...args);
+  };
+}
+
 const mountApp = () => {
   const rootContainer = document.getElementById('root');