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/go.opentelemetry.io/auto/sdk/internal/telemetry/scope.go

@@ -0,0 +1,67 @@
+// Copyright The OpenTelemetry Authors
+// SPDX-License-Identifier: Apache-2.0
+
+package telemetry
+
+import (
+	"bytes"
+	"encoding/json"
+	"errors"
+	"fmt"
+	"io"
+)
+
+// Scope is the identifying values of the instrumentation scope.
+type Scope struct {
+	Name         string `json:"name,omitempty"`
+	Version      string `json:"version,omitempty"`
+	Attrs        []Attr `json:"attributes,omitempty"`
+	DroppedAttrs uint32 `json:"droppedAttributesCount,omitempty"`
+}
+
+// UnmarshalJSON decodes the OTLP formatted JSON contained in data into r.
+func (s *Scope) UnmarshalJSON(data []byte) error {
+	decoder := json.NewDecoder(bytes.NewReader(data))
+
+	t, err := decoder.Token()
+	if err != nil {
+		return err
+	}
+	if t != json.Delim('{') {
+		return errors.New("invalid Scope type")
+	}
+
+	for decoder.More() {
+		keyIface, err := decoder.Token()
+		if err != nil {
+			if errors.Is(err, io.EOF) {
+				// Empty.
+				return nil
+			}
+			return err
+		}
+
+		key, ok := keyIface.(string)
+		if !ok {
+			return fmt.Errorf("invalid Scope field: %#v", keyIface)
+		}
+
+		switch key {
+		case "name":
+			err = decoder.Decode(&s.Name)
+		case "version":
+			err = decoder.Decode(&s.Version)
+		case "attributes":
+			err = decoder.Decode(&s.Attrs)
+		case "droppedAttributesCount", "dropped_attributes_count":
+			err = decoder.Decode(&s.DroppedAttrs)
+		default:
+			// Skip unknown.
+		}
+
+		if err != nil {
+			return err
+		}
+	}
+	return nil
+}