🐛(frontend) normalize thrown values into proper Error instances

LiveKit can surface raw DOM events (for example WebSocket "error"
events, whose only enumerable key is `isTrusted`) instead of Error
instances.

When such a value ends up being captured, our error reporting logs
it as "Event: Event captured as exception with keys: isTrusted",
which is unhelpful and hides the real cause.

Add a small helper that normalizes any unknown thrown or emitted
value into a proper Error, preserving the original payload as
context.

Fixes 01997b9a-db63-7fc2-8fe4-f21dd7fd608d.

src/frontend/src/features/rooms/components/Conference.tsx

@@ -37,6 +37,7 @@ import { notifyAutoMutedOnJoin } from '@/features/notifications/utils'
 import { useSnapshot } from 'valtio'
 import { userPreferencesStore } from '@/stores/userPreferences'
 import { userStore } from '@/stores/user'
+import { asError } from '../utils/error'
 
 export const Conference = ({
   roomId,
@@ -235,7 +236,7 @@ export const Conference = ({
             backgroundColor: 'primaryDark.50 !important',
           })}
           onError={(e) => {
-            posthog.captureException(e)
+            posthog.captureException(asError(e))
           }}
           onConnected={async () => {
             if (!apiConfig) return

src/frontend/src/features/rooms/utils/error.ts

@@ -0,0 +1,9 @@
+export const asError = (value: unknown): Error => {
+  if (value instanceof Error) return value
+  if (value instanceof Event) {
+    return new Error(
+      `Unhandled event "${value.type}" from ${value.target?.constructor.name ?? 'unknown'}`
+    )
+  }
+  return new Error(String(value))
+}