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/reflect/protodesc/desc_init.go

@@ -69,9 +69,7 @@ func (r descsByName) initMessagesDeclarations(mds []*descriptorpb.DescriptorProt
 		if m.L0, err = r.makeBase(m, parent, md.GetName(), i, sb); err != nil {
 			return nil, err
 		}
-		if m.Base.L0.ParentFile.Syntax() == protoreflect.Editions {
-			m.L1.EditionFeatures = mergeEditionFeatures(parent, md.GetOptions().GetFeatures())
-		}
+		m.L1.EditionFeatures = mergeEditionFeatures(parent, md.GetOptions().GetFeatures())
 		if opts := md.GetOptions(); opts != nil {
 			opts = proto.Clone(opts).(*descriptorpb.MessageOptions)
 			m.L2.Options = func() protoreflect.ProtoMessage { return opts }
@@ -146,13 +144,15 @@ func (r descsByName) initFieldsFromDescriptorProto(fds []*descriptorpb.FieldDesc
 		if f.L0, err = r.makeBase(f, parent, fd.GetName(), i, sb); err != nil {
 			return nil, err
 		}
+		f.L1.EditionFeatures = mergeEditionFeatures(parent, fd.GetOptions().GetFeatures())
 		f.L1.IsProto3Optional = fd.GetProto3Optional()
 		if opts := fd.GetOptions(); opts != nil {
 			opts = proto.Clone(opts).(*descriptorpb.FieldOptions)
 			f.L1.Options = func() protoreflect.ProtoMessage { return opts }
 			f.L1.IsWeak = opts.GetWeak()
-			f.L1.HasPacked = opts.Packed != nil
-			f.L1.IsPacked = opts.GetPacked()
+			if opts.Packed != nil {
+				f.L1.EditionFeatures.IsPacked = opts.GetPacked()
+			}
 		}
 		f.L1.Number = protoreflect.FieldNumber(fd.GetNumber())
 		f.L1.Cardinality = protoreflect.Cardinality(fd.GetLabel())
@@ -163,32 +163,12 @@ func (r descsByName) initFieldsFromDescriptorProto(fds []*descriptorpb.FieldDesc
 			f.L1.StringName.InitJSON(fd.GetJsonName())
 		}
 
-		if f.Base.L0.ParentFile.Syntax() == protoreflect.Editions {
-			f.L1.EditionFeatures = mergeEditionFeatures(parent, fd.GetOptions().GetFeatures())
+		if f.L1.EditionFeatures.IsLegacyRequired {
+			f.L1.Cardinality = protoreflect.Required
+		}
 
-			if f.L1.EditionFeatures.IsLegacyRequired {
-				f.L1.Cardinality = protoreflect.Required
-			}
-			// We reuse the existing field because the old option `[packed =
-			// true]` is mutually exclusive with the editions feature.
-			if canBePacked(fd) {
-				f.L1.HasPacked = true
-				f.L1.IsPacked = f.L1.EditionFeatures.IsPacked
-			}
-
-			// We pretend this option is always explicitly set because the only
-			// use of HasEnforceUTF8 is to determine whether to use EnforceUTF8
-			// or to return the appropriate default.
-			// When using editions we either parse the option or resolve the
-			// appropriate default here (instead of later when this option is
-			// requested from the descriptor).
-			// In proto2/proto3 syntax HasEnforceUTF8 might be false.
-			f.L1.HasEnforceUTF8 = true
-			f.L1.EnforceUTF8 = f.L1.EditionFeatures.IsUTF8Validated
-
-			if f.L1.Kind == protoreflect.MessageKind && f.L1.EditionFeatures.IsDelimitedEncoded {
-				f.L1.Kind = protoreflect.GroupKind
-			}
+		if f.L1.Kind == protoreflect.MessageKind && f.L1.EditionFeatures.IsDelimitedEncoded {
+			f.L1.Kind = protoreflect.GroupKind
 		}
 	}
 	return fs, nil
@@ -201,12 +181,10 @@ func (r descsByName) initOneofsFromDescriptorProto(ods []*descriptorpb.OneofDesc
 		if o.L0, err = r.makeBase(o, parent, od.GetName(), i, sb); err != nil {
 			return nil, err
 		}
+		o.L1.EditionFeatures = mergeEditionFeatures(parent, od.GetOptions().GetFeatures())
 		if opts := od.GetOptions(); opts != nil {
 			opts = proto.Clone(opts).(*descriptorpb.OneofOptions)
 			o.L1.Options = func() protoreflect.ProtoMessage { return opts }
-			if parent.Syntax() == protoreflect.Editions {
-				o.L1.EditionFeatures = mergeEditionFeatures(parent, opts.GetFeatures())
-			}
 		}
 	}
 	return os, nil
@@ -220,10 +198,13 @@ func (r descsByName) initExtensionDeclarations(xds []*descriptorpb.FieldDescript
 		if x.L0, err = r.makeBase(x, parent, xd.GetName(), i, sb); err != nil {
 			return nil, err
 		}
+		x.L1.EditionFeatures = mergeEditionFeatures(parent, xd.GetOptions().GetFeatures())
 		if opts := xd.GetOptions(); opts != nil {
 			opts = proto.Clone(opts).(*descriptorpb.FieldOptions)
 			x.L2.Options = func() protoreflect.ProtoMessage { return opts }
-			x.L2.IsPacked = opts.GetPacked()
+			if opts.Packed != nil {
+				x.L1.EditionFeatures.IsPacked = opts.GetPacked()
+			}
 		}
 		x.L1.Number = protoreflect.FieldNumber(xd.GetNumber())
 		x.L1.Cardinality = protoreflect.Cardinality(xd.GetLabel())