feat: add Apple Container support with comprehensive documentation and dev tools

Add native Apple Container support for better performance on macOS while
maintaining full Docker compatibility. Enhance documentation with memory system
details, development guidelines, and sandbox setup instructions. Improve dev
experience with container image pre-pulling and unified cleanup tools.

Key changes:
- Auto-detect and prefer Apple Container on macOS with Docker fallback
- Add APPLE_CONTAINER.md with complete usage and troubleshooting guide
- Document memory system architecture in CLAUDE.md
- Add make setup-sandbox for pre-pulling container images
- Create cleanup-containers.sh for cross-runtime container cleanup
- Update all related documentation (README, SETUP, config examples)

Co-Authored-By: Claude Sonnet 4.5 <noreply@anthropic.com>

README.md

@@ -41,18 +41,25 @@ If you prefer running services locally:
    make install
    ```
 
-3. **Start services**:
+3. **(Optional) Pre-pull sandbox image**:
+   ```bash
+   # Recommended if using Docker/Container-based sandbox
+   make setup-sandbox
+   ```
+
+4. **Start services**:
    ```bash
    make dev
    ```
 
-4. **Access**: http://localhost:2026
+5. **Access**: http://localhost:2026
 
 See [CONTRIBUTING.md](CONTRIBUTING.md) for detailed local development guide.
 
 ## Features
 
 - 🤖 **LangGraph-based Agents** - Multi-agent orchestration with sophisticated workflows
+- 🧠 **Persistent Memory** - LLM-powered context retention across conversations with automatic fact extraction
 - 🔧 **Model Context Protocol (MCP)** - Extensible tool integration
 - 🎯 **Skills System** - Reusable agent capabilities
 - 🛡️ **Sandbox Execution** - Safe code execution environment