Phase 3: Implement Core Task Execution Engine (v0.4.0)

This commit implements Phase 3 of the CHORUS task execution engine development plan,
replacing the mock implementation with a real AI-powered task execution system.

## Major Components Added:

### TaskExecutionEngine (pkg/execution/engine.go)
- Complete AI-powered task execution orchestration
- Bridges AI providers (Phase 1) with execution sandboxes (Phase 2)
- Configurable execution strategies and resource management
- Comprehensive task result processing and artifact handling
- Real-time metrics and monitoring integration

### Task Coordinator Integration (coordinator/task_coordinator.go)
- Replaced mock time.Sleep(10s) implementation with real AI execution
- Added initializeExecutionEngine() method for setup
- Integrated AI-powered execution with fallback to mock when needed
- Enhanced task result processing with execution metadata
- Improved task type detection and context building

### Key Features:
- **AI-Powered Execution**: Tasks are now processed by AI providers with appropriate role-based routing
- **Sandbox Integration**: Commands generated by AI are executed in secure Docker containers
- **Artifact Management**: Files and outputs generated during execution are properly captured
- **Performance Monitoring**: Detailed metrics tracking AI response time, sandbox execution time, and resource usage
- **Fallback Resilience**: Graceful fallback to mock execution when AI/sandbox systems are unavailable
- **Comprehensive Error Handling**: Proper error handling and logging throughout the execution pipeline

### Technical Implementation:
- Task execution requests are converted to AI prompts with contextual information
- AI responses are parsed to extract executable commands and file artifacts
- Commands are executed in isolated Docker containers with resource limits
- Results are aggregated with execution metrics and returned to the coordinator
- Full integration maintains backward compatibility while adding real execution capability

This completes the core execution engine and enables CHORUS agents to perform real AI-powered task execution
instead of simulated work, representing a major milestone in the autonomous agent capability.

🤖 Generated with [Claude Code](https://claude.ai/code)

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

Makefile

@@ -5,7 +5,7 @@
 BINARY_NAME_AGENT = chorus-agent
 BINARY_NAME_HAP = chorus-hap
 BINARY_NAME_COMPAT = chorus
-VERSION ?= 0.3.0
+VERSION ?= 0.4.0
 COMMIT_HASH ?= $(shell git rev-parse --short HEAD 2>/dev/null || echo "unknown")
 BUILD_DATE ?= $(shell date -u '+%Y-%m-%d_%H:%M:%S')