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/internal/global/instruments.go

@@ -1,16 +1,5 @@
 // Copyright The OpenTelemetry Authors
-//
-// Licensed under the Apache License, Version 2.0 (the "License");
-// you may not use this file except in compliance with the License.
-// You may obtain a copy of the License at
-//
-//     http://www.apache.org/licenses/LICENSE-2.0
-//
-// Unless required by applicable law or agreed to in writing, software
-// distributed under the License is distributed on an "AS IS" BASIS,
-// WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
-// See the License for the specific language governing permissions and
-// limitations under the License.
+// SPDX-License-Identifier: Apache-2.0
 
 package global // import "go.opentelemetry.io/otel/internal/global"
 
@@ -24,7 +13,7 @@ import (
 
 // unwrapper unwraps to return the underlying instrument implementation.
 type unwrapper interface {
-	Unwrap() metric.Observable
+	unwrap() metric.Observable
 }
 
 type afCounter struct {
@@ -34,11 +23,13 @@ type afCounter struct {
 	name string
 	opts []metric.Float64ObservableCounterOption
 
-	delegate atomic.Value //metric.Float64ObservableCounter
+	delegate atomic.Value // metric.Float64ObservableCounter
 }
 
-var _ unwrapper = (*afCounter)(nil)
-var _ metric.Float64ObservableCounter = (*afCounter)(nil)
+var (
+	_ unwrapper                       = (*afCounter)(nil)
+	_ metric.Float64ObservableCounter = (*afCounter)(nil)
+)
 
 func (i *afCounter) setDelegate(m metric.Meter) {
 	ctr, err := m.Float64ObservableCounter(i.name, i.opts...)
@@ -49,7 +40,7 @@ func (i *afCounter) setDelegate(m metric.Meter) {
 	i.delegate.Store(ctr)
 }
 
-func (i *afCounter) Unwrap() metric.Observable {
+func (i *afCounter) unwrap() metric.Observable {
 	if ctr := i.delegate.Load(); ctr != nil {
 		return ctr.(metric.Float64ObservableCounter)
 	}
@@ -63,11 +54,13 @@ type afUpDownCounter struct {
 	name string
 	opts []metric.Float64ObservableUpDownCounterOption
 
-	delegate atomic.Value //metric.Float64ObservableUpDownCounter
+	delegate atomic.Value // metric.Float64ObservableUpDownCounter
 }
 
-var _ unwrapper = (*afUpDownCounter)(nil)
-var _ metric.Float64ObservableUpDownCounter = (*afUpDownCounter)(nil)
+var (
+	_ unwrapper                             = (*afUpDownCounter)(nil)
+	_ metric.Float64ObservableUpDownCounter = (*afUpDownCounter)(nil)
+)
 
 func (i *afUpDownCounter) setDelegate(m metric.Meter) {
 	ctr, err := m.Float64ObservableUpDownCounter(i.name, i.opts...)
@@ -78,7 +71,7 @@ func (i *afUpDownCounter) setDelegate(m metric.Meter) {
 	i.delegate.Store(ctr)
 }
 
-func (i *afUpDownCounter) Unwrap() metric.Observable {
+func (i *afUpDownCounter) unwrap() metric.Observable {
 	if ctr := i.delegate.Load(); ctr != nil {
 		return ctr.(metric.Float64ObservableUpDownCounter)
 	}
@@ -92,11 +85,13 @@ type afGauge struct {
 	name string
 	opts []metric.Float64ObservableGaugeOption
 
-	delegate atomic.Value //metric.Float64ObservableGauge
+	delegate atomic.Value // metric.Float64ObservableGauge
 }
 
-var _ unwrapper = (*afGauge)(nil)
-var _ metric.Float64ObservableGauge = (*afGauge)(nil)
+var (
+	_ unwrapper                     = (*afGauge)(nil)
+	_ metric.Float64ObservableGauge = (*afGauge)(nil)
+)
 
 func (i *afGauge) setDelegate(m metric.Meter) {
 	ctr, err := m.Float64ObservableGauge(i.name, i.opts...)
@@ -107,7 +102,7 @@ func (i *afGauge) setDelegate(m metric.Meter) {
 	i.delegate.Store(ctr)
 }
 
-func (i *afGauge) Unwrap() metric.Observable {
+func (i *afGauge) unwrap() metric.Observable {
 	if ctr := i.delegate.Load(); ctr != nil {
 		return ctr.(metric.Float64ObservableGauge)
 	}
@@ -121,11 +116,13 @@ type aiCounter struct {
 	name string
 	opts []metric.Int64ObservableCounterOption
 
-	delegate atomic.Value //metric.Int64ObservableCounter
+	delegate atomic.Value // metric.Int64ObservableCounter
 }
 
-var _ unwrapper = (*aiCounter)(nil)
-var _ metric.Int64ObservableCounter = (*aiCounter)(nil)
+var (
+	_ unwrapper                     = (*aiCounter)(nil)
+	_ metric.Int64ObservableCounter = (*aiCounter)(nil)
+)
 
 func (i *aiCounter) setDelegate(m metric.Meter) {
 	ctr, err := m.Int64ObservableCounter(i.name, i.opts...)
@@ -136,7 +133,7 @@ func (i *aiCounter) setDelegate(m metric.Meter) {
 	i.delegate.Store(ctr)
 }
 
-func (i *aiCounter) Unwrap() metric.Observable {
+func (i *aiCounter) unwrap() metric.Observable {
 	if ctr := i.delegate.Load(); ctr != nil {
 		return ctr.(metric.Int64ObservableCounter)
 	}
@@ -150,11 +147,13 @@ type aiUpDownCounter struct {
 	name string
 	opts []metric.Int64ObservableUpDownCounterOption
 
-	delegate atomic.Value //metric.Int64ObservableUpDownCounter
+	delegate atomic.Value // metric.Int64ObservableUpDownCounter
 }
 
-var _ unwrapper = (*aiUpDownCounter)(nil)
-var _ metric.Int64ObservableUpDownCounter = (*aiUpDownCounter)(nil)
+var (
+	_ unwrapper                           = (*aiUpDownCounter)(nil)
+	_ metric.Int64ObservableUpDownCounter = (*aiUpDownCounter)(nil)
+)
 
 func (i *aiUpDownCounter) setDelegate(m metric.Meter) {
 	ctr, err := m.Int64ObservableUpDownCounter(i.name, i.opts...)
@@ -165,7 +164,7 @@ func (i *aiUpDownCounter) setDelegate(m metric.Meter) {
 	i.delegate.Store(ctr)
 }
 
-func (i *aiUpDownCounter) Unwrap() metric.Observable {
+func (i *aiUpDownCounter) unwrap() metric.Observable {
 	if ctr := i.delegate.Load(); ctr != nil {
 		return ctr.(metric.Int64ObservableUpDownCounter)
 	}
@@ -179,11 +178,13 @@ type aiGauge struct {
 	name string
 	opts []metric.Int64ObservableGaugeOption
 
-	delegate atomic.Value //metric.Int64ObservableGauge
+	delegate atomic.Value // metric.Int64ObservableGauge
 }
 
-var _ unwrapper = (*aiGauge)(nil)
-var _ metric.Int64ObservableGauge = (*aiGauge)(nil)
+var (
+	_ unwrapper                   = (*aiGauge)(nil)
+	_ metric.Int64ObservableGauge = (*aiGauge)(nil)
+)
 
 func (i *aiGauge) setDelegate(m metric.Meter) {
 	ctr, err := m.Int64ObservableGauge(i.name, i.opts...)
@@ -194,7 +195,7 @@ func (i *aiGauge) setDelegate(m metric.Meter) {
 	i.delegate.Store(ctr)
 }
 
-func (i *aiGauge) Unwrap() metric.Observable {
+func (i *aiGauge) unwrap() metric.Observable {
 	if ctr := i.delegate.Load(); ctr != nil {
 		return ctr.(metric.Int64ObservableGauge)
 	}
@@ -208,7 +209,7 @@ type sfCounter struct {
 	name string
 	opts []metric.Float64CounterOption
 
-	delegate atomic.Value //metric.Float64Counter
+	delegate atomic.Value // metric.Float64Counter
 }
 
 var _ metric.Float64Counter = (*sfCounter)(nil)
@@ -234,7 +235,7 @@ type sfUpDownCounter struct {
 	name string
 	opts []metric.Float64UpDownCounterOption
 
-	delegate atomic.Value //metric.Float64UpDownCounter
+	delegate atomic.Value // metric.Float64UpDownCounter
 }
 
 var _ metric.Float64UpDownCounter = (*sfUpDownCounter)(nil)
@@ -260,7 +261,7 @@ type sfHistogram struct {
 	name string
 	opts []metric.Float64HistogramOption
 
-	delegate atomic.Value //metric.Float64Histogram
+	delegate atomic.Value // metric.Float64Histogram
 }
 
 var _ metric.Float64Histogram = (*sfHistogram)(nil)
@@ -280,13 +281,39 @@ func (i *sfHistogram) Record(ctx context.Context, x float64, opts ...metric.Reco
 	}
 }
 
+type sfGauge struct {
+	embedded.Float64Gauge
+
+	name string
+	opts []metric.Float64GaugeOption
+
+	delegate atomic.Value // metric.Float64Gauge
+}
+
+var _ metric.Float64Gauge = (*sfGauge)(nil)
+
+func (i *sfGauge) setDelegate(m metric.Meter) {
+	ctr, err := m.Float64Gauge(i.name, i.opts...)
+	if err != nil {
+		GetErrorHandler().Handle(err)
+		return
+	}
+	i.delegate.Store(ctr)
+}
+
+func (i *sfGauge) Record(ctx context.Context, x float64, opts ...metric.RecordOption) {
+	if ctr := i.delegate.Load(); ctr != nil {
+		ctr.(metric.Float64Gauge).Record(ctx, x, opts...)
+	}
+}
+
 type siCounter struct {
 	embedded.Int64Counter
 
 	name string
 	opts []metric.Int64CounterOption
 
-	delegate atomic.Value //metric.Int64Counter
+	delegate atomic.Value // metric.Int64Counter
 }
 
 var _ metric.Int64Counter = (*siCounter)(nil)
@@ -312,7 +339,7 @@ type siUpDownCounter struct {
 	name string
 	opts []metric.Int64UpDownCounterOption
 
-	delegate atomic.Value //metric.Int64UpDownCounter
+	delegate atomic.Value // metric.Int64UpDownCounter
 }
 
 var _ metric.Int64UpDownCounter = (*siUpDownCounter)(nil)
@@ -338,7 +365,7 @@ type siHistogram struct {
 	name string
 	opts []metric.Int64HistogramOption
 
-	delegate atomic.Value //metric.Int64Histogram
+	delegate atomic.Value // metric.Int64Histogram
 }
 
 var _ metric.Int64Histogram = (*siHistogram)(nil)
@@ -357,3 +384,29 @@ func (i *siHistogram) Record(ctx context.Context, x int64, opts ...metric.Record
 		ctr.(metric.Int64Histogram).Record(ctx, x, opts...)
 	}
 }
+
+type siGauge struct {
+	embedded.Int64Gauge
+
+	name string
+	opts []metric.Int64GaugeOption
+
+	delegate atomic.Value // metric.Int64Gauge
+}
+
+var _ metric.Int64Gauge = (*siGauge)(nil)
+
+func (i *siGauge) setDelegate(m metric.Meter) {
+	ctr, err := m.Int64Gauge(i.name, i.opts...)
+	if err != nil {
+		GetErrorHandler().Handle(err)
+		return
+	}
+	i.delegate.Store(ctr)
+}
+
+func (i *siGauge) Record(ctx context.Context, x int64, opts ...metric.RecordOption) {
+	if ctr := i.delegate.Load(); ctr != nil {
+		ctr.(metric.Int64Gauge).Record(ctx, x, opts...)
+	}
+}