Implement background sync and session preservation

[BillSteinUNB]

Summary

Improve background handling to preserve session state and allow syncing when the app is in the background, ensuring users don't lose work and stay up-to-date.

Context

Currently, when WhisperCode goes to the background, there can be issues with:

• Losing session state
• Interrupted file syncing
• Missing server updates
• Connection drops

Better background handling would make the app more reliable and reduce friction for users who frequently switch between apps.

Goals

1. Preserve Session State

   • Save current session context when backgrounded
   • Restore seamlessly when returning to foreground
   • Don't lose any in-progress work

2. Background Sync

   • Continue syncing file changes when possible
   • Update session status in background
   • Queue actions that need to be sent to server

3. Better Reconnection

   • Automatically reconnect to server when returning to foreground
   • Handle network transitions gracefully (WiFi <-> Cellular)
   • Don't require manual refresh

4. Background Tasks

   • Complete any pending operations before suspension
   • Save local changes to persist
   • Handle iOS memory pressure gracefully

Technical Considerations

• Use iOS background task APIs (BGTaskScheduler, etc.)
• Implement proper state persistence
• Handle "nominal" background time efficiently
• Consider notification-based updates as alternative

Related

• Add server-driven push notifications via OpenCode plugin #5: Server-driven push notifications (complements background sync)

Labels

• enhancement
• reliability