Implement Thread-Safe Agent Memory System with Multiple Storage Backends

[zhangfengcdt]

Overview

This PR addresses thread safety issues in the agent memory system by implementing thread-safe wrappers and adding support for multiple storage backends (Git, InMemory, File) while maintaining a clean, unified interface.

Problem Statement

The original src/agent/versioned_persistence.rs had thread safety limitations due to the gix library containing RefCell components that prevent Sync trait implementation, making it unsuitable for multi-threaded contexts.

Solution Architecture

Implemented a comprehensive thread-safe memory system with multiple storage backend options using Arc<Mutex<>> pattern for synchronized access.

Storage Backend Options

Backend	Use Case	Features
ThreadSafeGit	Production with version control	Full git history, branching, commits
ThreadSafeInMemory	Testing, caching	Fast access, ephemeral storage
ThreadSafeFile	Local persistence	File-based storage without git overhead
Simple	Basic use cases	Lightweight, no threading
ThreadSafe (Legacy)	Compatibility	Maintains existing API

Key Features Implemented

✅ Thread Safety: All storage backends are thread-safe using Arc<Mutex<>> pattern
✅ Multiple Backends: Support for Git, InMemory, File, and Simple storage
✅ Unified Interface: Consistent API across all storage types
✅ Git Integration: Full version control with branching and commit history
✅ Backward Compatibility: Existing APIs preserved
✅ Performance Options: Choose between speed (InMemory) and durability (Git/File)