Phase 2: Implement Execution Environment Abstraction (v0.3.0)

This commit implements Phase 2 of the CHORUS Task Execution Engine development plan,
providing a comprehensive execution environment abstraction layer with Docker
container sandboxing support.

## New Features

### Core Sandbox Interface
- Comprehensive ExecutionSandbox interface with isolated task execution
- Support for command execution, file I/O, environment management
- Resource usage monitoring and sandbox lifecycle management
- Standardized error handling with SandboxError types and categories

### Docker Container Sandbox Implementation
- Full Docker API integration with secure container creation
- Transparent repository mounting with configurable read/write access
- Advanced security policies with capability dropping and privilege controls
- Comprehensive resource limits (CPU, memory, disk, processes, file handles)
- Support for tmpfs mounts, masked paths, and read-only bind mounts
- Container lifecycle management with proper cleanup and health monitoring

### Security & Resource Management
- Configurable security policies with SELinux, AppArmor, and Seccomp support
- Fine-grained capability management with secure defaults
- Network isolation options with configurable DNS and proxy settings
- Resource monitoring with real-time CPU, memory, and network usage tracking
- Comprehensive ulimits configuration for process and file handle limits

### Repository Integration
- Seamless repository mounting from local paths to container workspaces
- Git configuration support with user credentials and global settings
- File inclusion/exclusion patterns for selective repository access
- Configurable permissions and ownership for mounted repositories

### Testing Infrastructure
- Comprehensive test suite with 60+ test cases covering all functionality
- Docker integration tests with Alpine Linux containers (skipped in short mode)
- Mock sandbox implementation for unit testing without Docker dependencies
- Security policy validation tests with read-only filesystem enforcement
- Resource usage monitoring and cleanup verification tests

## Technical Details

### Dependencies Added
- github.com/docker/docker v28.4.0+incompatible - Docker API client
- github.com/docker/go-connections v0.6.0 - Docker connection utilities
- github.com/docker/go-units v0.5.0 - Docker units and formatting
- Associated Docker API dependencies for complete container management

### Architecture
- Interface-driven design enabling multiple sandbox implementations
- Comprehensive configuration structures for all sandbox aspects
- Resource usage tracking with detailed metrics collection
- Error handling with retryable error classification
- Proper cleanup and resource management throughout sandbox lifecycle

### Compatibility
- Maintains backward compatibility with existing CHORUS architecture
- Designed for future integration with Phase 3 Core Task Execution Engine
- Extensible design supporting additional sandbox implementations (VM, process)

This Phase 2 implementation provides the foundation for secure, isolated task
execution that will be integrated with the AI model providers from Phase 1
in the upcoming Phase 3 development.

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

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

vendor/golang.org/x/sys/cpu/cpu.go

@@ -72,6 +72,9 @@ var X86 struct {
 	HasSSSE3            bool // Supplemental streaming SIMD extension 3
 	HasSSE41            bool // Streaming SIMD extension 4 and 4.1
 	HasSSE42            bool // Streaming SIMD extension 4 and 4.2
+	HasAVXIFMA          bool // Advanced vector extension Integer Fused Multiply Add
+	HasAVXVNNI          bool // Advanced vector extension Vector Neural Network Instructions
+	HasAVXVNNIInt8      bool // Advanced vector extension Vector Neural Network Int8 instructions
 	_                   CacheLinePad
 }
 
@@ -146,6 +149,18 @@ var ARM struct {
 	_           CacheLinePad
 }
 
+// The booleans in Loong64 contain the correspondingly named cpu feature bit.
+// The struct is padded to avoid false sharing.
+var Loong64 struct {
+	_         CacheLinePad
+	HasLSX    bool // support 128-bit vector extension
+	HasLASX   bool // support 256-bit vector extension
+	HasCRC32  bool // support CRC instruction
+	HasLAM_BH bool // support AM{SWAP/ADD}[_DB].{B/H} instruction
+	HasLAMCAS bool // support AMCAS[_DB].{B/H/W/D} instruction
+	_         CacheLinePad
+}
+
 // MIPS64X contains the supported CPU features of the current mips64/mips64le
 // platforms. If the current platform is not mips64/mips64le or the current
 // operating system is not Linux then all feature flags are false.
@@ -217,6 +232,17 @@ var RISCV64 struct {
 	HasZba            bool // Address generation instructions extension
 	HasZbb            bool // Basic bit-manipulation extension
 	HasZbs            bool // Single-bit instructions extension
+	HasZvbb           bool // Vector Basic Bit-manipulation
+	HasZvbc           bool // Vector Carryless Multiplication
+	HasZvkb           bool // Vector Cryptography Bit-manipulation
+	HasZvkt           bool // Vector Data-Independent Execution Latency
+	HasZvkg           bool // Vector GCM/GMAC
+	HasZvkn           bool // NIST Algorithm Suite (AES/SHA256/SHA512)
+	HasZvknc          bool // NIST Algorithm Suite with carryless multiply
+	HasZvkng          bool // NIST Algorithm Suite with GCM
+	HasZvks           bool // ShangMi Algorithm Suite
+	HasZvksc          bool // ShangMi Algorithm Suite with carryless multiplication
+	HasZvksg          bool // ShangMi Algorithm Suite with GCM
 	_                 CacheLinePad
 }