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/trace/noop.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 trace // import "go.opentelemetry.io/otel/trace"
 
@@ -19,44 +8,48 @@ import (
 
 	"go.opentelemetry.io/otel/attribute"
 	"go.opentelemetry.io/otel/codes"
+	"go.opentelemetry.io/otel/trace/embedded"
 )
 
 // NewNoopTracerProvider returns an implementation of TracerProvider that
 // performs no operations. The Tracer and Spans created from the returned
 // TracerProvider also perform no operations.
+//
+// Deprecated: Use [go.opentelemetry.io/otel/trace/noop.NewTracerProvider]
+// instead.
 func NewNoopTracerProvider() TracerProvider {
 	return noopTracerProvider{}
 }
 
-type noopTracerProvider struct{}
+type noopTracerProvider struct{ embedded.TracerProvider }
 
 var _ TracerProvider = noopTracerProvider{}
 
 // Tracer returns noop implementation of Tracer.
-func (p noopTracerProvider) Tracer(string, ...TracerOption) Tracer {
+func (noopTracerProvider) Tracer(string, ...TracerOption) Tracer {
 	return noopTracer{}
 }
 
 // noopTracer is an implementation of Tracer that performs no operations.
-type noopTracer struct{}
+type noopTracer struct{ embedded.Tracer }
 
 var _ Tracer = noopTracer{}
 
 // Start carries forward a non-recording Span, if one is present in the context, otherwise it
 // creates a no-op Span.
-func (t noopTracer) Start(ctx context.Context, name string, _ ...SpanStartOption) (context.Context, Span) {
+func (noopTracer) Start(ctx context.Context, _ string, _ ...SpanStartOption) (context.Context, Span) {
 	span := SpanFromContext(ctx)
 	if _, ok := span.(nonRecordingSpan); !ok {
 		// span is likely already a noopSpan, but let's be sure
-		span = noopSpan{}
+		span = noopSpanInstance
 	}
 	return ContextWithSpan(ctx, span), span
 }
 
 // noopSpan is an implementation of Span that performs no operations.
-type noopSpan struct{}
+type noopSpan struct{ embedded.Span }
 
-var _ Span = noopSpan{}
+var noopSpanInstance Span = noopSpan{}
 
 // SpanContext returns an empty span context.
 func (noopSpan) SpanContext() SpanContext { return SpanContext{} }
@@ -82,8 +75,31 @@ func (noopSpan) RecordError(error, ...EventOption) {}
 // AddEvent does nothing.
 func (noopSpan) AddEvent(string, ...EventOption) {}
 
+// AddLink does nothing.
+func (noopSpan) AddLink(Link) {}
+
 // SetName does nothing.
 func (noopSpan) SetName(string) {}
 
 // TracerProvider returns a no-op TracerProvider.
-func (noopSpan) TracerProvider() TracerProvider { return noopTracerProvider{} }
+func (s noopSpan) TracerProvider() TracerProvider {
+	return s.tracerProvider(autoInstEnabled)
+}
+
+// autoInstEnabled defines if the auto-instrumentation SDK is enabled.
+//
+// The auto-instrumentation is expected to overwrite this value to true when it
+// attaches to the process.
+var autoInstEnabled = new(bool)
+
+// tracerProvider return a noopTracerProvider if autoEnabled is false,
+// otherwise it will return a TracerProvider from the sdk package used in
+// auto-instrumentation.
+//
+//go:noinline
+func (noopSpan) tracerProvider(autoEnabled *bool) TracerProvider {
+	if *autoEnabled {
+		return newAutoTracerProvider()
+	}
+	return noopTracerProvider{}
+}