feat: add slog structured logging

Co-Authored-By: Claude Fable 5 <noreply@anthropic.com>

internal/service/workspace_service.go

@@ -1,6 +1,8 @@
 package service
 
 import (
+	"log/slog"
+
 	"codespace/internal/process"
 	"codespace/internal/workspace"
 )
@@ -9,16 +11,26 @@ import (
 type WorkspaceService struct {
 	workspaces workspace.Manager
 	processes  process.Manager
+	logger     *slog.Logger
 }
 
 // NewWorkspaceService creates a WorkspaceService.
-func NewWorkspaceService(workspaces workspace.Manager, processes process.Manager) *WorkspaceService {
-	return &WorkspaceService{workspaces: workspaces, processes: processes}
+// If lg is nil, slog.Default() is used.
+func NewWorkspaceService(workspaces workspace.Manager, processes process.Manager, lg *slog.Logger) *WorkspaceService {
+	if lg == nil {
+		lg = slog.Default()
+	}
+	return &WorkspaceService{workspaces: workspaces, processes: processes, logger: lg}
 }
 
 // Create creates a new workspace.
 func (s *WorkspaceService) Create(id string) (*workspace.Workspace, error) {
-	return s.workspaces.Create(id)
+	ws, err := s.workspaces.Create(id)
+	if err != nil {
+		return nil, err
+	}
+	s.logger.Info("workspace created", "workspace_id", id)
+	return ws, nil
 }
 
 // Get retrieves a workspace by id.
@@ -30,7 +42,13 @@ func (s *WorkspaceService) Get(id string) (*workspace.Workspace, error) {
 func (s *WorkspaceService) Delete(id string) error {
 	status := s.processes.Status(id)
 	if status.Running {
-		_ = s.processes.Stop(id)
+		if err := s.processes.Stop(id); err != nil {
+			s.logger.Error("failed to stop workspace process before delete", "workspace_id", id, "error", err)
+		}
 	}
-	return s.workspaces.Delete(id)
+	if err := s.workspaces.Delete(id); err != nil {
+		return err
+	}
+	s.logger.Info("workspace deleted", "workspace_id", id)
+	return nil
 }