fix(observability): convert root rewrite to redirect; suppress Write permission noise

/ was served via rewrite (/en content at / URL). Nextra reads the locale
from window.location.pathname, gets empty string from "/".split("/")[1],
then calls Intl with "" → "Invalid language tag". 20+ errors per day.
Fix: 301 redirect / → /en so the browser URL reflects the actual locale.

Also adds Write permission denied / Permission denied to access property
to IGNORED_PATTERNS — Chrome Android WebView/extension noise (file=None).

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

Author: Mlaz-code

components/PostHogProvider.tsx

@@ -28,6 +28,10 @@ const IGNORED_PATTERNS = [
   /Hydration failed/,
   /There was an error while hydrating/,
   /Text content did not match/,
+  // "Write permission denied." / "Permission denied to access property" — Chrome
+  // Android WebView sandbox / browser extension. No source file captured.
+  /Write permission denied/,
+  /Permission denied to access property/,
 ]
 
 function shouldIgnore(message: string): boolean {

vercel.json

@@ -5,6 +5,11 @@
   "cleanUrls": true,
   "ignoreCommand": "git diff --quiet HEAD^ HEAD -- app/ components/ content/ public/ scripts/ next.config.mjs proxy.ts mdx-components.tsx package.json vercel.json",
   "redirects": [
+    {
+      "source": "/",
+      "destination": "/en",
+      "permanent": true
+    },
     {
       "source": "/en/sdks/sharpapi.d.ts",
       "destination": "/en/sdks/typescript",
@@ -172,10 +177,6 @@
     }
   ],
   "rewrites": [
-    {
-      "source": "/",
-      "destination": "/en"
-    },
     {
       "source": "/ingest/static/:path*",
       "destination": "https://us-assets.i.posthog.com/static/:path*"