fix: use unified classifier in intent classification API when available (#320)

The Classification API's /api/v1/classify/intent endpoint was returning
placeholder "general" category responses with 0.5 confidence instead of
performing actual classification using the unified classifier.

Changes:
- Update handleIntentClassification() to check for unified classifier availability first
- Use ClassifyIntentUnified() when unified classifier is available
- Fall back to legacy ClassifyIntent() when unified classifier not available
- Maintain backward compatibility with existing API contract

This resolves the issue where the single classification API always returned
hardcoded placeholder responses instead of performing actual BERT-based
classification.

Fixes #303

Signed-off-by: Yossi Ovadia <[email protected]>
Co-authored-by: Huamin Chen <[email protected]>

Author: yossiovadia

src/semantic-router/pkg/api/server.go

@@ -232,7 +232,16 @@ func (s *ClassificationAPIServer) handleIntentClassification(w http.ResponseWrit
 		return
 	}
 
-	response, err := s.classificationSvc.ClassifyIntent(req)
+	// Use unified classifier if available, otherwise fall back to legacy
+	var response *services.IntentResponse
+	var err error
+
+	if s.classificationSvc.HasUnifiedClassifier() {
+		response, err = s.classificationSvc.ClassifyIntentUnified(req)
+	} else {
+		response, err = s.classificationSvc.ClassifyIntent(req)
+	}
+
 	if err != nil {
 		s.writeErrorResponse(w, http.StatusInternalServerError, "CLASSIFICATION_ERROR", err.Error())
 		return