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>

go.mod

@@ -1,6 +1,6 @@
 module chorus
 
-go 1.23
+go 1.23.0
 
 toolchain go1.24.5
 
@@ -8,6 +8,9 @@ require (
 	filippo.io/age v1.2.1
 	github.com/blevesearch/bleve/v2 v2.5.3
 	github.com/chorus-services/backbeat v0.0.0-00010101000000-000000000000
+	github.com/docker/docker v28.4.0+incompatible
+	github.com/docker/go-connections v0.6.0
+	github.com/docker/go-units v0.5.0
 	github.com/go-redis/redis/v8 v8.11.5
 	github.com/google/uuid v1.6.0
 	github.com/gorilla/mux v1.8.1
@@ -22,13 +25,14 @@ require (
 	github.com/robfig/cron/v3 v3.0.1
 	github.com/sashabaranov/go-openai v1.41.1
 	github.com/sony/gobreaker v0.5.0
-	github.com/stretchr/testify v1.10.0
+	github.com/stretchr/testify v1.11.1
 	github.com/syndtr/goleveldb v1.0.0
 	golang.org/x/crypto v0.24.0
 	gopkg.in/yaml.v3 v3.0.1
 )
 
 require (
+	github.com/Microsoft/go-winio v0.6.2 // indirect
 	github.com/RoaringBitmap/roaring/v2 v2.4.5 // indirect
 	github.com/benbjohnson/clock v1.3.5 // indirect
 	github.com/beorn7/perks v1.0.1 // indirect
@@ -52,16 +56,19 @@ require (
 	github.com/blevesearch/zapx/v16 v16.2.4 // indirect
 	github.com/cespare/xxhash/v2 v2.2.0 // indirect
 	github.com/containerd/cgroups v1.1.0 // indirect
+	github.com/containerd/errdefs v1.0.0 // indirect
+	github.com/containerd/errdefs/pkg v0.3.0 // indirect
 	github.com/coreos/go-systemd/v22 v22.5.0 // indirect
 	github.com/davecgh/go-spew v1.1.1 // indirect
 	github.com/davidlazar/go-crypto v0.0.0-20200604182044-b73af7476f6c // indirect
 	github.com/decred/dcrd/dcrec/secp256k1/v4 v4.2.0 // indirect
 	github.com/dgryski/go-rendezvous v0.0.0-20200823014737-9f7001d12a5f // indirect
-	github.com/docker/go-units v0.5.0 // indirect
+	github.com/distribution/reference v0.6.0 // indirect
 	github.com/elastic/gosigar v0.14.2 // indirect
+	github.com/felixge/httpsnoop v1.0.4 // indirect
 	github.com/flynn/noise v1.0.0 // indirect
 	github.com/francoispqt/gojay v1.2.13 // indirect
-	github.com/go-logr/logr v1.2.4 // indirect
+	github.com/go-logr/logr v1.4.3 // indirect
 	github.com/go-logr/stdr v1.2.2 // indirect
 	github.com/go-task/slim-sprig v0.0.0-20230315185526-52ccab3ef572 // indirect
 	github.com/godbus/dbus/v5 v5.1.0 // indirect
@@ -106,6 +113,7 @@ require (
 	github.com/mikioh/tcpinfo v0.0.0-20190314235526-30a79bb1804b // indirect
 	github.com/mikioh/tcpopt v0.0.0-20190314235656-172688c1accc // indirect
 	github.com/minio/sha256-simd v1.0.1 // indirect
+	github.com/moby/docker-image-spec v1.3.1 // indirect
 	github.com/modern-go/concurrent v0.0.0-20180306012644-bacd9c7ef1dd // indirect
 	github.com/modern-go/reflect2 v1.0.2 // indirect
 	github.com/mr-tron/base58 v1.2.0 // indirect
@@ -122,6 +130,8 @@ require (
 	github.com/nats-io/nkeys v0.4.7 // indirect
 	github.com/nats-io/nuid v1.0.1 // indirect
 	github.com/onsi/ginkgo/v2 v2.13.0 // indirect
+	github.com/opencontainers/go-digest v1.0.0 // indirect
+	github.com/opencontainers/image-spec v1.1.1 // indirect
 	github.com/opencontainers/runtime-spec v1.1.0 // indirect
 	github.com/opentracing/opentracing-go v1.2.0 // indirect
 	github.com/pbnjay/memory v0.0.0-20210728143218-7b4eea64cf58 // indirect
@@ -140,9 +150,11 @@ require (
 	github.com/whyrusleeping/go-keyspace v0.0.0-20160322163242-5b898ac5add1 // indirect
 	go.etcd.io/bbolt v1.4.0 // indirect
 	go.opencensus.io v0.24.0 // indirect
-	go.opentelemetry.io/otel v1.16.0 // indirect
-	go.opentelemetry.io/otel/metric v1.16.0 // indirect
-	go.opentelemetry.io/otel/trace v1.16.0 // indirect
+	go.opentelemetry.io/auto/sdk v1.1.0 // indirect
+	go.opentelemetry.io/contrib/instrumentation/net/http/otelhttp v0.63.0 // indirect
+	go.opentelemetry.io/otel v1.38.0 // indirect
+	go.opentelemetry.io/otel/metric v1.38.0 // indirect
+	go.opentelemetry.io/otel/trace v1.38.0 // indirect
 	go.uber.org/dig v1.17.1 // indirect
 	go.uber.org/fx v1.20.1 // indirect
 	go.uber.org/mock v0.3.0 // indirect
@@ -152,11 +164,11 @@ require (
 	golang.org/x/mod v0.18.0 // indirect
 	golang.org/x/net v0.26.0 // indirect
 	golang.org/x/sync v0.10.0 // indirect
-	golang.org/x/sys v0.29.0 // indirect
+	golang.org/x/sys v0.35.0 // indirect
 	golang.org/x/text v0.16.0 // indirect
 	golang.org/x/tools v0.22.0 // indirect
 	gonum.org/v1/gonum v0.13.0 // indirect
-	google.golang.org/protobuf v1.33.0 // indirect
+	google.golang.org/protobuf v1.34.2 // indirect
 	lukechampine.com/blake3 v1.2.1 // indirect
 )