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/impl/codec_field.go

@@ -233,9 +233,15 @@ func sizeMessageInfo(p pointer, f *coderFieldInfo, opts marshalOptions) int {
 }
 
 func appendMessageInfo(b []byte, p pointer, f *coderFieldInfo, opts marshalOptions) ([]byte, error) {
+	calculatedSize := f.mi.sizePointer(p.Elem(), opts)
 	b = protowire.AppendVarint(b, f.wiretag)
-	b = protowire.AppendVarint(b, uint64(f.mi.sizePointer(p.Elem(), opts)))
-	return f.mi.marshalAppendPointer(b, p.Elem(), opts)
+	b = protowire.AppendVarint(b, uint64(calculatedSize))
+	before := len(b)
+	b, err := f.mi.marshalAppendPointer(b, p.Elem(), opts)
+	if measuredSize := len(b) - before; calculatedSize != measuredSize && err == nil {
+		return nil, errors.MismatchedSizeCalculation(calculatedSize, measuredSize)
+	}
+	return b, err
 }
 
 func consumeMessageInfo(b []byte, p pointer, wtyp protowire.Type, f *coderFieldInfo, opts unmarshalOptions) (out unmarshalOutput, err error) {
@@ -262,14 +268,21 @@ func isInitMessageInfo(p pointer, f *coderFieldInfo) error {
 	return f.mi.checkInitializedPointer(p.Elem())
 }
 
-func sizeMessage(m proto.Message, tagsize int, _ marshalOptions) int {
-	return protowire.SizeBytes(proto.Size(m)) + tagsize
+func sizeMessage(m proto.Message, tagsize int, opts marshalOptions) int {
+	return protowire.SizeBytes(opts.Options().Size(m)) + tagsize
 }
 
 func appendMessage(b []byte, m proto.Message, wiretag uint64, opts marshalOptions) ([]byte, error) {
+	mopts := opts.Options()
+	calculatedSize := mopts.Size(m)
 	b = protowire.AppendVarint(b, wiretag)
-	b = protowire.AppendVarint(b, uint64(proto.Size(m)))
-	return opts.Options().MarshalAppend(b, m)
+	b = protowire.AppendVarint(b, uint64(calculatedSize))
+	before := len(b)
+	b, err := mopts.MarshalAppend(b, m)
+	if measuredSize := len(b) - before; calculatedSize != measuredSize && err == nil {
+		return nil, errors.MismatchedSizeCalculation(calculatedSize, measuredSize)
+	}
+	return b, err
 }
 
 func consumeMessage(b []byte, m proto.Message, wtyp protowire.Type, opts unmarshalOptions) (out unmarshalOutput, err error) {
@@ -405,8 +418,8 @@ func consumeGroupType(b []byte, p pointer, wtyp protowire.Type, f *coderFieldInf
 	return f.mi.unmarshalPointer(b, p.Elem(), f.num, opts)
 }
 
-func sizeGroup(m proto.Message, tagsize int, _ marshalOptions) int {
-	return 2*tagsize + proto.Size(m)
+func sizeGroup(m proto.Message, tagsize int, opts marshalOptions) int {
+	return 2*tagsize + opts.Options().Size(m)
 }
 
 func appendGroup(b []byte, m proto.Message, wiretag uint64, opts marshalOptions) ([]byte, error) {
@@ -482,10 +495,14 @@ func appendMessageSliceInfo(b []byte, p pointer, f *coderFieldInfo, opts marshal
 		b = protowire.AppendVarint(b, f.wiretag)
 		siz := f.mi.sizePointer(v, opts)
 		b = protowire.AppendVarint(b, uint64(siz))
+		before := len(b)
 		b, err = f.mi.marshalAppendPointer(b, v, opts)
 		if err != nil {
 			return b, err
 		}
+		if measuredSize := len(b) - before; siz != measuredSize {
+			return nil, errors.MismatchedSizeCalculation(siz, measuredSize)
+		}
 	}
 	return b, nil
 }
@@ -520,28 +537,34 @@ func isInitMessageSliceInfo(p pointer, f *coderFieldInfo) error {
 	return nil
 }
 
-func sizeMessageSlice(p pointer, goType reflect.Type, tagsize int, _ marshalOptions) int {
+func sizeMessageSlice(p pointer, goType reflect.Type, tagsize int, opts marshalOptions) int {
+	mopts := opts.Options()
 	s := p.PointerSlice()
 	n := 0
 	for _, v := range s {
 		m := asMessage(v.AsValueOf(goType.Elem()))
-		n += protowire.SizeBytes(proto.Size(m)) + tagsize
+		n += protowire.SizeBytes(mopts.Size(m)) + tagsize
 	}
 	return n
 }
 
 func appendMessageSlice(b []byte, p pointer, wiretag uint64, goType reflect.Type, opts marshalOptions) ([]byte, error) {
+	mopts := opts.Options()
 	s := p.PointerSlice()
 	var err error
 	for _, v := range s {
 		m := asMessage(v.AsValueOf(goType.Elem()))
 		b = protowire.AppendVarint(b, wiretag)
-		siz := proto.Size(m)
+		siz := mopts.Size(m)
 		b = protowire.AppendVarint(b, uint64(siz))
-		b, err = opts.Options().MarshalAppend(b, m)
+		before := len(b)
+		b, err = mopts.MarshalAppend(b, m)
 		if err != nil {
 			return b, err
 		}
+		if measuredSize := len(b) - before; siz != measuredSize {
+			return nil, errors.MismatchedSizeCalculation(siz, measuredSize)
+		}
 	}
 	return b, nil
 }
@@ -582,11 +605,12 @@ func isInitMessageSlice(p pointer, goType reflect.Type) error {
 // Slices of messages
 
 func sizeMessageSliceValue(listv protoreflect.Value, tagsize int, opts marshalOptions) int {
+	mopts := opts.Options()
 	list := listv.List()
 	n := 0
 	for i, llen := 0, list.Len(); i < llen; i++ {
 		m := list.Get(i).Message().Interface()
-		n += protowire.SizeBytes(proto.Size(m)) + tagsize
+		n += protowire.SizeBytes(mopts.Size(m)) + tagsize
 	}
 	return n
 }
@@ -597,13 +621,17 @@ func appendMessageSliceValue(b []byte, listv protoreflect.Value, wiretag uint64,
 	for i, llen := 0, list.Len(); i < llen; i++ {
 		m := list.Get(i).Message().Interface()
 		b = protowire.AppendVarint(b, wiretag)
-		siz := proto.Size(m)
+		siz := mopts.Size(m)
 		b = protowire.AppendVarint(b, uint64(siz))
+		before := len(b)
 		var err error
 		b, err = mopts.MarshalAppend(b, m)
 		if err != nil {
 			return b, err
 		}
+		if measuredSize := len(b) - before; siz != measuredSize {
+			return nil, errors.MismatchedSizeCalculation(siz, measuredSize)
+		}
 	}
 	return b, nil
 }
@@ -651,11 +679,12 @@ var coderMessageSliceValue = valueCoderFuncs{
 }
 
 func sizeGroupSliceValue(listv protoreflect.Value, tagsize int, opts marshalOptions) int {
+	mopts := opts.Options()
 	list := listv.List()
 	n := 0
 	for i, llen := 0, list.Len(); i < llen; i++ {
 		m := list.Get(i).Message().Interface()
-		n += 2*tagsize + proto.Size(m)
+		n += 2*tagsize + mopts.Size(m)
 	}
 	return n
 }
@@ -738,12 +767,13 @@ func makeGroupSliceFieldCoder(fd protoreflect.FieldDescriptor, ft reflect.Type)
 	}
 }
 
-func sizeGroupSlice(p pointer, messageType reflect.Type, tagsize int, _ marshalOptions) int {
+func sizeGroupSlice(p pointer, messageType reflect.Type, tagsize int, opts marshalOptions) int {
+	mopts := opts.Options()
 	s := p.PointerSlice()
 	n := 0
 	for _, v := range s {
 		m := asMessage(v.AsValueOf(messageType.Elem()))
-		n += 2*tagsize + proto.Size(m)
+		n += 2*tagsize + mopts.Size(m)
 	}
 	return n
 }