Add engine-scoped backend registration

profiles.go

@@ -6,14 +6,10 @@ import (
 	"fmt"
 	"strings"
 
-	"gitea.maximumdirect.net/eric/promptkit/internal/backend"
 	"gitea.maximumdirect.net/eric/promptkit/internal/domain"
 	"gitea.maximumdirect.net/eric/promptkit/internal/profile"
 )
 
-// BackendOpenRouter identifies Promptkit's built-in OpenRouter backend.
-const BackendOpenRouter = backend.OpenRouterID
-
 // OpenAICompatibleProfile returns an ordinary in-memory Profile for an
 // OpenAI-compatible chat-completions endpoint.
 //