- Introduced `TaskConfig` struct to manage task-related configurations.
- Implemented `TaskTool` for creating and managing subagents for complex tasks.
- Added `TaskSession` and `TaskRepository` for handling task sessions and persistence.
- Created `DefaultSubAgentRuntime` to execute tasks with timeout and history support.
- Enhanced `ToolContext` to include `subagent_description` for better context tracking.
- Implemented error handling for task execution and session management.
- Updated `ToolRegistryFactory` to register task tools conditionally based on configuration.
- Added prompt builders for subagent tasks to improve interaction clarity.
