Add intelligent image selection for development environments

Integrate chorus-dev-images repository with automatic language detection
and appropriate development container selection.

New features:
- ImageSelector for automatic language-to-image mapping
- Language detection from task context, description, and repository
- Standardized workspace environment variables
- Support for 7 development environments (Rust, Go, Python, Node, Java, C++)

Changes:
- pkg/execution/images.go (new): Image selection and language detection logic
- pkg/execution/engine.go: Modified createSandboxConfig to use ImageSelector

This ensures agents automatically get the right tools for their tasks without
manual configuration.

Related: https://gitea.chorus.services/tony/chorus-dev-images

🤖 Generated with Claude Code (https://claude.com/claude-code)

Co-Authored-By: Claude <noreply@anthropic.com>

pkg/execution/engine.go

@@ -395,15 +395,25 @@ func (e *DefaultTaskExecutionEngine) executeSandboxCommands(ctx context.Context,
 
 // createSandboxConfig creates a sandbox configuration from task requirements
 func (e *DefaultTaskExecutionEngine) createSandboxConfig(request *TaskExecutionRequest) *SandboxConfig {
+	// Use image selector to choose appropriate development environment
+	imageSelector := NewImageSelector()
+	selectedImage := imageSelector.SelectImageForTask(request)
+
 	config := &SandboxConfig{
 		Type:         "docker",
-		Image:        "alpine:latest",
+		Image:        selectedImage, // Auto-selected based on task language
 		Architecture: "amd64",
-		WorkingDir:   "/workspace",
+		WorkingDir:   "/workspace/data", // Use standardized workspace structure
 		Timeout:      5 * time.Minute,
 		Environment:  make(map[string]string),
 	}
 
+	// Add standardized workspace environment variables
+	config.Environment["WORKSPACE_ROOT"] = "/workspace"
+	config.Environment["WORKSPACE_INPUT"] = "/workspace/input"
+	config.Environment["WORKSPACE_DATA"] = "/workspace/data"
+	config.Environment["WORKSPACE_OUTPUT"] = "/workspace/output"
+
 	// Apply defaults from engine config
 	if e.config.SandboxDefaults != nil {
 		if e.config.SandboxDefaults.Image != "" {