♻️(frontend) refactor useConnectionObserver to track session time

Add session duration tracking and consolidate all disconnect events
(including client-initiated) with timing data for comprehensive
connection analytics.

src/frontend/src/features/rooms/livekit/hooks/useConnectionObserver.ts

@@ -1,17 +1,25 @@
 import { useRoomContext } from '@livekit/components-react'
-import { useEffect } from 'react'
+import { useEffect, useRef } from 'react'
 import { DisconnectReason, RoomEvent } from 'livekit-client'
 import { useIsAnalyticsEnabled } from '@/features/analytics/hooks/useIsAnalyticsEnabled'
 import posthog from 'posthog-js'
 
 export const useConnectionObserver = () => {
   const room = useRoomContext()
+  const connectionStartTimeRef = useRef<number | null>(null)
 
   const isAnalyticsEnabled = useIsAnalyticsEnabled()
 
   useEffect(() => {
     if (!isAnalyticsEnabled) return
 
+    const handleConnection = () => {
+      // Preserve original connection timestamp across reconnections to measure
+      // total session duration from first connect to final disconnect.
+      if (connectionStartTimeRef.current != null) return
+      connectionStartTimeRef.current = Date.now()
+    }
+
     const handleReconnect = () => {
       posthog.capture('reconnect-event')
     }
@@ -19,16 +27,34 @@ export const useConnectionObserver = () => {
     const handleDisconnect = (
       disconnectReason: DisconnectReason | undefined
     ) => {
-      if (disconnectReason == DisconnectReason.CLIENT_INITIATED) return
+      const connectionEndTime = Date.now()
+
       posthog.capture('disconnect-event', {
-        reason: disconnectReason && DisconnectReason[disconnectReason],
+        // Calculate total session duration from first connection to final disconnect
+        // This duration is sensitive to refreshing the page.
+        sessionDuration: connectionStartTimeRef.current
+          ? connectionEndTime - connectionStartTimeRef.current
+          : -1,
+        reason: disconnectReason
+          ? DisconnectReason[disconnectReason]
+          : 'UNKNOWN',
       })
     }
+
+    room.on(RoomEvent.Connected, handleConnection)
     room.on(RoomEvent.Disconnected, handleDisconnect)
     room.on(RoomEvent.Reconnecting, handleReconnect)
+
     return () => {
+      room.off(RoomEvent.Connected, handleConnection)
       room.off(RoomEvent.Disconnected, handleDisconnect)
       room.off(RoomEvent.Reconnecting, handleReconnect)
     }
   }, [room, isAnalyticsEnabled])
+
+  useEffect(() => {
+    return () => {
+      connectionStartTimeRef.current = null
+    }
+  }, [])
 }