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/github.com/stretchr/testify/assert/assertion_compare.go

@@ -390,7 +390,8 @@ func Greater(t TestingT, e1 interface{}, e2 interface{}, msgAndArgs ...interface
 	if h, ok := t.(tHelper); ok {
 		h.Helper()
 	}
-	return compareTwoValues(t, e1, e2, []compareResult{compareGreater}, "\"%v\" is not greater than \"%v\"", msgAndArgs...)
+	failMessage := fmt.Sprintf("\"%v\" is not greater than \"%v\"", e1, e2)
+	return compareTwoValues(t, e1, e2, []compareResult{compareGreater}, failMessage, msgAndArgs...)
 }
 
 // GreaterOrEqual asserts that the first element is greater than or equal to the second
@@ -403,7 +404,8 @@ func GreaterOrEqual(t TestingT, e1 interface{}, e2 interface{}, msgAndArgs ...in
 	if h, ok := t.(tHelper); ok {
 		h.Helper()
 	}
-	return compareTwoValues(t, e1, e2, []compareResult{compareGreater, compareEqual}, "\"%v\" is not greater than or equal to \"%v\"", msgAndArgs...)
+	failMessage := fmt.Sprintf("\"%v\" is not greater than or equal to \"%v\"", e1, e2)
+	return compareTwoValues(t, e1, e2, []compareResult{compareGreater, compareEqual}, failMessage, msgAndArgs...)
 }
 
 // Less asserts that the first element is less than the second
@@ -415,7 +417,8 @@ func Less(t TestingT, e1 interface{}, e2 interface{}, msgAndArgs ...interface{})
 	if h, ok := t.(tHelper); ok {
 		h.Helper()
 	}
-	return compareTwoValues(t, e1, e2, []compareResult{compareLess}, "\"%v\" is not less than \"%v\"", msgAndArgs...)
+	failMessage := fmt.Sprintf("\"%v\" is not less than \"%v\"", e1, e2)
+	return compareTwoValues(t, e1, e2, []compareResult{compareLess}, failMessage, msgAndArgs...)
 }
 
 // LessOrEqual asserts that the first element is less than or equal to the second
@@ -428,7 +431,8 @@ func LessOrEqual(t TestingT, e1 interface{}, e2 interface{}, msgAndArgs ...inter
 	if h, ok := t.(tHelper); ok {
 		h.Helper()
 	}
-	return compareTwoValues(t, e1, e2, []compareResult{compareLess, compareEqual}, "\"%v\" is not less than or equal to \"%v\"", msgAndArgs...)
+	failMessage := fmt.Sprintf("\"%v\" is not less than or equal to \"%v\"", e1, e2)
+	return compareTwoValues(t, e1, e2, []compareResult{compareLess, compareEqual}, failMessage, msgAndArgs...)
 }
 
 // Positive asserts that the specified element is positive
@@ -440,7 +444,8 @@ func Positive(t TestingT, e interface{}, msgAndArgs ...interface{}) bool {
 		h.Helper()
 	}
 	zero := reflect.Zero(reflect.TypeOf(e))
-	return compareTwoValues(t, e, zero.Interface(), []compareResult{compareGreater}, "\"%v\" is not positive", msgAndArgs...)
+	failMessage := fmt.Sprintf("\"%v\" is not positive", e)
+	return compareTwoValues(t, e, zero.Interface(), []compareResult{compareGreater}, failMessage, msgAndArgs...)
 }
 
 // Negative asserts that the specified element is negative
@@ -452,7 +457,8 @@ func Negative(t TestingT, e interface{}, msgAndArgs ...interface{}) bool {
 		h.Helper()
 	}
 	zero := reflect.Zero(reflect.TypeOf(e))
-	return compareTwoValues(t, e, zero.Interface(), []compareResult{compareLess}, "\"%v\" is not negative", msgAndArgs...)
+	failMessage := fmt.Sprintf("\"%v\" is not negative", e)
+	return compareTwoValues(t, e, zero.Interface(), []compareResult{compareLess}, failMessage, msgAndArgs...)
 }
 
 func compareTwoValues(t TestingT, e1 interface{}, e2 interface{}, allowedComparesResults []compareResult, failMessage string, msgAndArgs ...interface{}) bool {
@@ -468,11 +474,11 @@ func compareTwoValues(t TestingT, e1 interface{}, e2 interface{}, allowedCompare
 
 	compareResult, isComparable := compare(e1, e2, e1Kind)
 	if !isComparable {
-		return Fail(t, fmt.Sprintf("Can not compare type \"%s\"", reflect.TypeOf(e1)), msgAndArgs...)
+		return Fail(t, fmt.Sprintf(`Can not compare type "%T"`, e1), msgAndArgs...)
 	}
 
 	if !containsValue(allowedComparesResults, compareResult) {
-		return Fail(t, fmt.Sprintf(failMessage, e1, e2), msgAndArgs...)
+		return Fail(t, failMessage, msgAndArgs...)
 	}
 
 	return true