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/otel/attribute/internal/attribute.go

@@ -0,0 +1,96 @@
+// Copyright The OpenTelemetry Authors
+// SPDX-License-Identifier: Apache-2.0
+
+/*
+Package attribute provide several helper functions for some commonly used
+logic of processing attributes.
+*/
+package attribute // import "go.opentelemetry.io/otel/attribute/internal"
+
+import (
+	"reflect"
+)
+
+// BoolSliceValue converts a bool slice into an array with same elements as slice.
+func BoolSliceValue(v []bool) any {
+	var zero bool
+	cp := reflect.New(reflect.ArrayOf(len(v), reflect.TypeOf(zero))).Elem()
+	reflect.Copy(cp, reflect.ValueOf(v))
+	return cp.Interface()
+}
+
+// Int64SliceValue converts an int64 slice into an array with same elements as slice.
+func Int64SliceValue(v []int64) any {
+	var zero int64
+	cp := reflect.New(reflect.ArrayOf(len(v), reflect.TypeOf(zero))).Elem()
+	reflect.Copy(cp, reflect.ValueOf(v))
+	return cp.Interface()
+}
+
+// Float64SliceValue converts a float64 slice into an array with same elements as slice.
+func Float64SliceValue(v []float64) any {
+	var zero float64
+	cp := reflect.New(reflect.ArrayOf(len(v), reflect.TypeOf(zero))).Elem()
+	reflect.Copy(cp, reflect.ValueOf(v))
+	return cp.Interface()
+}
+
+// StringSliceValue converts a string slice into an array with same elements as slice.
+func StringSliceValue(v []string) any {
+	var zero string
+	cp := reflect.New(reflect.ArrayOf(len(v), reflect.TypeOf(zero))).Elem()
+	reflect.Copy(cp, reflect.ValueOf(v))
+	return cp.Interface()
+}
+
+// AsBoolSlice converts a bool array into a slice into with same elements as array.
+func AsBoolSlice(v any) []bool {
+	rv := reflect.ValueOf(v)
+	if rv.Type().Kind() != reflect.Array {
+		return nil
+	}
+	cpy := make([]bool, rv.Len())
+	if len(cpy) > 0 {
+		_ = reflect.Copy(reflect.ValueOf(cpy), rv)
+	}
+	return cpy
+}
+
+// AsInt64Slice converts an int64 array into a slice into with same elements as array.
+func AsInt64Slice(v any) []int64 {
+	rv := reflect.ValueOf(v)
+	if rv.Type().Kind() != reflect.Array {
+		return nil
+	}
+	cpy := make([]int64, rv.Len())
+	if len(cpy) > 0 {
+		_ = reflect.Copy(reflect.ValueOf(cpy), rv)
+	}
+	return cpy
+}
+
+// AsFloat64Slice converts a float64 array into a slice into with same elements as array.
+func AsFloat64Slice(v any) []float64 {
+	rv := reflect.ValueOf(v)
+	if rv.Type().Kind() != reflect.Array {
+		return nil
+	}
+	cpy := make([]float64, rv.Len())
+	if len(cpy) > 0 {
+		_ = reflect.Copy(reflect.ValueOf(cpy), rv)
+	}
+	return cpy
+}
+
+// AsStringSlice converts a string array into a slice into with same elements as array.
+func AsStringSlice(v any) []string {
+	rv := reflect.ValueOf(v)
+	if rv.Type().Kind() != reflect.Array {
+		return nil
+	}
+	cpy := make([]string, rv.Len())
+	if len(cpy) > 0 {
+		_ = reflect.Copy(reflect.ValueOf(cpy), rv)
+	}
+	return cpy
+}