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/contrib/instrumentation/net/http/otelhttp/handler.go

@@ -0,0 +1,238 @@
+// Copyright The OpenTelemetry Authors
+// SPDX-License-Identifier: Apache-2.0
+
+package otelhttp // import "go.opentelemetry.io/contrib/instrumentation/net/http/otelhttp"
+
+import (
+	"net/http"
+	"time"
+
+	"github.com/felixge/httpsnoop"
+	"go.opentelemetry.io/otel"
+	"go.opentelemetry.io/otel/attribute"
+	"go.opentelemetry.io/otel/propagation"
+	"go.opentelemetry.io/otel/trace"
+
+	"go.opentelemetry.io/contrib/instrumentation/net/http/otelhttp/internal/request"
+	"go.opentelemetry.io/contrib/instrumentation/net/http/otelhttp/internal/semconv"
+)
+
+// middleware is an http middleware which wraps the next handler in a span.
+type middleware struct {
+	operation string
+	server    string
+
+	tracer             trace.Tracer
+	propagators        propagation.TextMapPropagator
+	spanStartOptions   []trace.SpanStartOption
+	readEvent          bool
+	writeEvent         bool
+	filters            []Filter
+	spanNameFormatter  func(string, *http.Request) string
+	publicEndpoint     bool
+	publicEndpointFn   func(*http.Request) bool
+	metricAttributesFn func(*http.Request) []attribute.KeyValue
+
+	semconv semconv.HTTPServer
+}
+
+func defaultHandlerFormatter(operation string, _ *http.Request) string {
+	return operation
+}
+
+// NewHandler wraps the passed handler in a span named after the operation and
+// enriches it with metrics.
+func NewHandler(handler http.Handler, operation string, opts ...Option) http.Handler {
+	return NewMiddleware(operation, opts...)(handler)
+}
+
+// NewMiddleware returns a tracing and metrics instrumentation middleware.
+// The handler returned by the middleware wraps a handler
+// in a span named after the operation and enriches it with metrics.
+func NewMiddleware(operation string, opts ...Option) func(http.Handler) http.Handler {
+	h := middleware{
+		operation: operation,
+	}
+
+	defaultOpts := []Option{
+		WithSpanOptions(trace.WithSpanKind(trace.SpanKindServer)),
+		WithSpanNameFormatter(defaultHandlerFormatter),
+	}
+
+	c := newConfig(append(defaultOpts, opts...)...)
+	h.configure(c)
+
+	return func(next http.Handler) http.Handler {
+		return http.HandlerFunc(func(w http.ResponseWriter, r *http.Request) {
+			h.serveHTTP(w, r, next)
+		})
+	}
+}
+
+func (h *middleware) configure(c *config) {
+	h.tracer = c.Tracer
+	h.propagators = c.Propagators
+	h.spanStartOptions = c.SpanStartOptions
+	h.readEvent = c.ReadEvent
+	h.writeEvent = c.WriteEvent
+	h.filters = c.Filters
+	h.spanNameFormatter = c.SpanNameFormatter
+	h.publicEndpoint = c.PublicEndpoint
+	h.publicEndpointFn = c.PublicEndpointFn
+	h.server = c.ServerName
+	h.semconv = semconv.NewHTTPServer(c.Meter)
+	h.metricAttributesFn = c.MetricAttributesFn
+}
+
+// serveHTTP sets up tracing and calls the given next http.Handler with the span
+// context injected into the request context.
+func (h *middleware) serveHTTP(w http.ResponseWriter, r *http.Request, next http.Handler) {
+	requestStartTime := time.Now()
+	for _, f := range h.filters {
+		if !f(r) {
+			// Simply pass through to the handler if a filter rejects the request
+			next.ServeHTTP(w, r)
+			return
+		}
+	}
+
+	ctx := h.propagators.Extract(r.Context(), propagation.HeaderCarrier(r.Header))
+	opts := []trace.SpanStartOption{
+		trace.WithAttributes(h.semconv.RequestTraceAttrs(h.server, r, semconv.RequestTraceAttrsOpts{})...),
+	}
+
+	opts = append(opts, h.spanStartOptions...)
+	if h.publicEndpoint || (h.publicEndpointFn != nil && h.publicEndpointFn(r.WithContext(ctx))) {
+		opts = append(opts, trace.WithNewRoot())
+		// Linking incoming span context if any for public endpoint.
+		if s := trace.SpanContextFromContext(ctx); s.IsValid() && s.IsRemote() {
+			opts = append(opts, trace.WithLinks(trace.Link{SpanContext: s}))
+		}
+	}
+
+	tracer := h.tracer
+
+	if tracer == nil {
+		if span := trace.SpanFromContext(r.Context()); span.SpanContext().IsValid() {
+			tracer = newTracer(span.TracerProvider())
+		} else {
+			tracer = newTracer(otel.GetTracerProvider())
+		}
+	}
+
+	if startTime := StartTimeFromContext(ctx); !startTime.IsZero() {
+		opts = append(opts, trace.WithTimestamp(startTime))
+		requestStartTime = startTime
+	}
+
+	ctx, span := tracer.Start(ctx, h.spanNameFormatter(h.operation, r), opts...)
+	defer span.End()
+
+	readRecordFunc := func(int64) {}
+	if h.readEvent {
+		readRecordFunc = func(n int64) {
+			span.AddEvent("read", trace.WithAttributes(ReadBytesKey.Int64(n)))
+		}
+	}
+
+	// if request body is nil or NoBody, we don't want to mutate the body as it
+	// will affect the identity of it in an unforeseeable way because we assert
+	// ReadCloser fulfills a certain interface and it is indeed nil or NoBody.
+	bw := request.NewBodyWrapper(r.Body, readRecordFunc)
+	if r.Body != nil && r.Body != http.NoBody {
+		r.Body = bw
+	}
+
+	writeRecordFunc := func(int64) {}
+	if h.writeEvent {
+		writeRecordFunc = func(n int64) {
+			span.AddEvent("write", trace.WithAttributes(WroteBytesKey.Int64(n)))
+		}
+	}
+
+	rww := request.NewRespWriterWrapper(w, writeRecordFunc)
+
+	// Wrap w to use our ResponseWriter methods while also exposing
+	// other interfaces that w may implement (http.CloseNotifier,
+	// http.Flusher, http.Hijacker, http.Pusher, io.ReaderFrom).
+
+	w = httpsnoop.Wrap(w, httpsnoop.Hooks{
+		Header: func(httpsnoop.HeaderFunc) httpsnoop.HeaderFunc {
+			return rww.Header
+		},
+		Write: func(httpsnoop.WriteFunc) httpsnoop.WriteFunc {
+			return rww.Write
+		},
+		WriteHeader: func(httpsnoop.WriteHeaderFunc) httpsnoop.WriteHeaderFunc {
+			return rww.WriteHeader
+		},
+		Flush: func(httpsnoop.FlushFunc) httpsnoop.FlushFunc {
+			return rww.Flush
+		},
+	})
+
+	labeler, found := LabelerFromContext(ctx)
+	if !found {
+		ctx = ContextWithLabeler(ctx, labeler)
+	}
+
+	r = r.WithContext(ctx)
+	next.ServeHTTP(w, r)
+
+	if r.Pattern != "" {
+		span.SetName(h.spanNameFormatter(h.operation, r))
+	}
+
+	statusCode := rww.StatusCode()
+	bytesWritten := rww.BytesWritten()
+	span.SetStatus(h.semconv.Status(statusCode))
+	span.SetAttributes(h.semconv.ResponseTraceAttrs(semconv.ResponseTelemetry{
+		StatusCode: statusCode,
+		ReadBytes:  bw.BytesRead(),
+		ReadError:  bw.Error(),
+		WriteBytes: bytesWritten,
+		WriteError: rww.Error(),
+	})...)
+
+	// Use floating point division here for higher precision (instead of Millisecond method).
+	elapsedTime := float64(time.Since(requestStartTime)) / float64(time.Millisecond)
+
+	metricAttributes := semconv.MetricAttributes{
+		Req:                  r,
+		StatusCode:           statusCode,
+		AdditionalAttributes: append(labeler.Get(), h.metricAttributesFromRequest(r)...),
+	}
+
+	h.semconv.RecordMetrics(ctx, semconv.ServerMetricData{
+		ServerName:       h.server,
+		ResponseSize:     bytesWritten,
+		MetricAttributes: metricAttributes,
+		MetricData: semconv.MetricData{
+			RequestSize: bw.BytesRead(),
+			ElapsedTime: elapsedTime,
+		},
+	})
+}
+
+func (h *middleware) metricAttributesFromRequest(r *http.Request) []attribute.KeyValue {
+	var attributeForRequest []attribute.KeyValue
+	if h.metricAttributesFn != nil {
+		attributeForRequest = h.metricAttributesFn(r)
+	}
+	return attributeForRequest
+}
+
+// WithRouteTag annotates spans and metrics with the provided route name
+// with HTTP route attribute.
+func WithRouteTag(route string, h http.Handler) http.Handler {
+	attr := semconv.NewHTTPServer(nil).Route(route)
+	return http.HandlerFunc(func(w http.ResponseWriter, r *http.Request) {
+		span := trace.SpanFromContext(r.Context())
+		span.SetAttributes(attr)
+
+		labeler, _ := LabelerFromContext(r.Context())
+		labeler.Add(attr)
+
+		h.ServeHTTP(w, r)
+	})
+}