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/github.com/go-logr/logr/logr.go

@@ -127,9 +127,9 @@ limitations under the License.
 // such a value can call its methods without having to check whether the
 // instance is ready for use.
 //
-// Calling methods with the null logger (Logger{}) as instance will crash
-// because it has no LogSink. Therefore this null logger should never be passed
-// around. For cases where passing a logger is optional, a pointer to Logger
+// The zero logger (= Logger{}) is identical to Discard() and discards all log
+// entries. Code that receives a Logger by value can simply call it, the methods
+// will never crash. For cases where passing a logger is optional, a pointer to Logger
 // should be used.
 //
 // # Key Naming Conventions
@@ -207,10 +207,6 @@ limitations under the License.
 // those.
 package logr
 
-import (
-	"context"
-)
-
 // New returns a new Logger instance.  This is primarily used by libraries
 // implementing LogSink, rather than end users.  Passing a nil sink will create
 // a Logger which discards all log lines.
@@ -258,6 +254,12 @@ type Logger struct {
 // Enabled tests whether this Logger is enabled.  For example, commandline
 // flags might be used to set the logging verbosity and disable some info logs.
 func (l Logger) Enabled() bool {
+	// Some implementations of LogSink look at the caller in Enabled (e.g.
+	// different verbosity levels per package or file), but we only pass one
+	// CallDepth in (via Init).  This means that all calls from Logger to the
+	// LogSink's Enabled, Info, and Error methods must have the same number of
+	// frames.  In other words, Logger methods can't call other Logger methods
+	// which call these LogSink methods unless we do it the same in all paths.
 	return l.sink != nil && l.sink.Enabled(l.level)
 }
 
@@ -267,11 +269,11 @@ func (l Logger) Enabled() bool {
 // line.  The key/value pairs can then be used to add additional variable
 // information.  The key/value pairs must alternate string keys and arbitrary
 // values.
-func (l Logger) Info(msg string, keysAndValues ...interface{}) {
+func (l Logger) Info(msg string, keysAndValues ...any) {
 	if l.sink == nil {
 		return
 	}
-	if l.Enabled() {
+	if l.sink.Enabled(l.level) { // see comment in Enabled
 		if withHelper, ok := l.sink.(CallStackHelperLogSink); ok {
 			withHelper.GetCallStackHelper()()
 		}
@@ -289,7 +291,7 @@ func (l Logger) Info(msg string, keysAndValues ...interface{}) {
 // while the err argument should be used to attach the actual error that
 // triggered this log line, if present. The err parameter is optional
 // and nil may be passed instead of an error instance.
-func (l Logger) Error(err error, msg string, keysAndValues ...interface{}) {
+func (l Logger) Error(err error, msg string, keysAndValues ...any) {
 	if l.sink == nil {
 		return
 	}
@@ -314,9 +316,16 @@ func (l Logger) V(level int) Logger {
 	return l
 }
 
+// GetV returns the verbosity level of the logger. If the logger's LogSink is
+// nil as in the Discard logger, this will always return 0.
+func (l Logger) GetV() int {
+	// 0 if l.sink nil because of the if check in V above.
+	return l.level
+}
+
 // WithValues returns a new Logger instance with additional key/value pairs.
 // See Info for documentation on how key/value pairs work.
-func (l Logger) WithValues(keysAndValues ...interface{}) Logger {
+func (l Logger) WithValues(keysAndValues ...any) Logger {
 	if l.sink == nil {
 		return l
 	}
@@ -397,45 +406,6 @@ func (l Logger) IsZero() bool {
 	return l.sink == nil
 }
 
-// contextKey is how we find Loggers in a context.Context.
-type contextKey struct{}
-
-// FromContext returns a Logger from ctx or an error if no Logger is found.
-func FromContext(ctx context.Context) (Logger, error) {
-	if v, ok := ctx.Value(contextKey{}).(Logger); ok {
-		return v, nil
-	}
-
-	return Logger{}, notFoundError{}
-}
-
-// notFoundError exists to carry an IsNotFound method.
-type notFoundError struct{}
-
-func (notFoundError) Error() string {
-	return "no logr.Logger was present"
-}
-
-func (notFoundError) IsNotFound() bool {
-	return true
-}
-
-// FromContextOrDiscard returns a Logger from ctx.  If no Logger is found, this
-// returns a Logger that discards all log messages.
-func FromContextOrDiscard(ctx context.Context) Logger {
-	if v, ok := ctx.Value(contextKey{}).(Logger); ok {
-		return v
-	}
-
-	return Discard()
-}
-
-// NewContext returns a new Context, derived from ctx, which carries the
-// provided Logger.
-func NewContext(ctx context.Context, logger Logger) context.Context {
-	return context.WithValue(ctx, contextKey{}, logger)
-}
-
 // RuntimeInfo holds information that the logr "core" library knows which
 // LogSinks might want to know.
 type RuntimeInfo struct {
@@ -467,15 +437,15 @@ type LogSink interface {
 	// The level argument is provided for optional logging.  This method will
 	// only be called when Enabled(level) is true. See Logger.Info for more
 	// details.
-	Info(level int, msg string, keysAndValues ...interface{})
+	Info(level int, msg string, keysAndValues ...any)
 
 	// Error logs an error, with the given message and key/value pairs as
 	// context.  See Logger.Error for more details.
-	Error(err error, msg string, keysAndValues ...interface{})
+	Error(err error, msg string, keysAndValues ...any)
 
 	// WithValues returns a new LogSink with additional key/value pairs.  See
 	// Logger.WithValues for more details.
-	WithValues(keysAndValues ...interface{}) LogSink
+	WithValues(keysAndValues ...any) LogSink
 
 	// WithName returns a new LogSink with the specified name appended.  See
 	// Logger.WithName for more details.
@@ -546,5 +516,5 @@ type Marshaler interface {
 	//     with exported fields
 	//
 	// It may return any value of any type.
-	MarshalLog() interface{}
+	MarshalLog() any
 }