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/google.golang.org/protobuf/internal/filedesc/editions.go

@@ -14,9 +14,13 @@ import (
 )
 
 var defaultsCache = make(map[Edition]EditionFeatures)
+var defaultsKeys = []Edition{}
 
 func init() {
 	unmarshalEditionDefaults(editiondefaults.Defaults)
+	SurrogateProto2.L1.EditionFeatures = getFeaturesFor(EditionProto2)
+	SurrogateProto3.L1.EditionFeatures = getFeaturesFor(EditionProto3)
+	SurrogateEdition2023.L1.EditionFeatures = getFeaturesFor(Edition2023)
 }
 
 func unmarshalGoFeature(b []byte, parent EditionFeatures) EditionFeatures {
@@ -104,12 +108,15 @@ func unmarshalEditionDefault(b []byte) {
 			v, m := protowire.ConsumeBytes(b)
 			b = b[m:]
 			switch num {
-			case genid.FeatureSetDefaults_FeatureSetEditionDefault_Features_field_number:
+			case genid.FeatureSetDefaults_FeatureSetEditionDefault_FixedFeatures_field_number:
+				fs = unmarshalFeatureSet(v, fs)
+			case genid.FeatureSetDefaults_FeatureSetEditionDefault_OverridableFeatures_field_number:
 				fs = unmarshalFeatureSet(v, fs)
 			}
 		}
 	}
 	defaultsCache[ed] = fs
+	defaultsKeys = append(defaultsKeys, ed)
 }
 
 func unmarshalEditionDefaults(b []byte) {
@@ -135,8 +142,15 @@ func unmarshalEditionDefaults(b []byte) {
 }
 
 func getFeaturesFor(ed Edition) EditionFeatures {
-	if def, ok := defaultsCache[ed]; ok {
-		return def
+	match := EditionUnknown
+	for _, key := range defaultsKeys {
+		if key > ed {
+			break
+		}
+		match = key
 	}
-	panic(fmt.Sprintf("unsupported edition: %v", ed))
+	if match == EditionUnknown {
+		panic(fmt.Sprintf("unsupported edition: %v", ed))
+	}
+	return defaultsCache[match]
 }