[Feature] Implement offline mode with sync capability

[coderabbitai]

Overview

Enable ThumbCode to work offline with automatic sync when online.

Current State

• No offline support
• App requires internet connection
• No sync mechanism

Requirements

• Implement offline detection
• Add local storage for: Projects/workspaces, Chat history, Pending changes, Agent tasks
• Build sync engine: Conflict resolution, Merge strategies, Queue management
• Add offline indicators in UI
• Implement optimistic updates
• Add background sync
• Handle auth token expiry
• Test offline scenarios
• Document offline capabilities

Success Criteria

• Full functionality offline
• Seamless sync when online
• No data loss
• Clear offline status

Priority: MEDIUM

Estimated Effort: 6-8 days

Dependencies: Git Service, State Management

Labels: feature, offline, priority:medium

Backlink: Related to PR #2

[jbdevprimary]

Closing — offline mode with sync is a significant engineering effort that requires:

• Sync conflict resolution strategy for git operations
• Local database for chat history and task state (IndexedDB/SQLite)
• Service worker for offline detection and background sync
• Optimistic update patterns throughout the UI

The Zustand stores already persist state client-side, providing basic data retention. Full offline git operations would require bundling isomorphic-git with a local filesystem adapter. This is a post-v1.0 feature that should be scoped into targeted sub-issues when prioritized.