fix: resolve Sentry hydration mismatch and suppress extension noise

website/src/components/ui/FadeIn.tsx

@@ -1,9 +1,24 @@
 'use client';
 import { motion, useReducedMotion } from 'framer-motion';
-import { ReactNode } from 'react';
+import { ReactNode, useState, useEffect, memo } from 'react';
 
-export function FadeIn({ children, delay = 0, className = '' }: { children: ReactNode; delay?: number; className?: string }) {
+export const FadeIn = memo(function FadeIn({ children, delay = 0, className = '' }: { children: ReactNode; delay?: number; className?: string }) {
   const shouldReduce = useReducedMotion();
+  const [isMounted, setIsMounted] = useState(false);
+
+  // Defer Framer Motion's initial state until after hydration. Without this,
+  // Framer Motion applies initial={{ opacity: 0 }} before React hydrates, causing
+  // the server-rendered HTML (opacity:1) to mismatch the client DOM (opacity:0).
+  useEffect(() => {
+    setIsMounted(true);
+  }, []);
+
+  if (!isMounted) {
+    // Server + hydration pass: render without Framer Motion so the DOM matches
+    // the server HTML exactly. No opacity/transform styles applied.
+    return <div className={className}>{children}</div>;
+  }
+
   return (
     <motion.div
       initial={{ opacity: 0, y: shouldReduce ? 0 : 16 }}
@@ -14,4 +29,4 @@ export function FadeIn({ children, delay = 0, className = '' }: { children: Reac
       {children}
     </motion.div>
   );
-}
+});

website/src/instrumentation-client.ts

@@ -12,6 +12,31 @@ Sentry.init({
   integrations: [
     Sentry.replayIntegration(),
   ],
+  beforeSend(event) {
+    const msg = event.exception?.values?.[0]?.value ?? "";
+
+    // Drop known browser-extension noise that cannot be fixed in app code:
+    //
+    // 1. "Cannot assign to read only property 'pushState'" — extensions
+    //    (Vue/Redux DevTools, privacy tools) wrap history.pushState before our
+    //    app loads, making it read-only. Not reproducible without the extension.
+    //
+    // 2. "Object Not Found Matching Id:N, MethodName:update" — Chrome DevTools
+    //    Protocol messages from extensions interacting with CodeMirror/Monaco.
+    //    The error originates outside our code and only affects a single session.
+    const isExtensionNoise =
+      msg.includes("Cannot assign to read only property 'pushState'") ||
+      msg.includes("Object Not Found Matching Id:");
+
+    if (isExtensionNoise) {
+      if (process.env.NODE_ENV === "development") {
+        console.debug("[Sentry] Suppressed extension noise:", msg);
+      }
+      return null;
+    }
+
+    return event;
+  },
 });
 
 export const onRouterTransitionStart = dsn