fix: select provider AFTER routing resolves model groups

Previously, provider selection happened on the raw client-requested model
name (e.g. 'dispatcher') which defaulted to OpenAI. After routing resolved
it to 'deepseek-v4-flash', the provider was never re-selected.

Now prefix-stripping + routing runs first, then selectProvider() picks
the correct provider based on the resolved concrete model.

internal/server/server.go

@@ -533,38 +533,7 @@ func (s *Server) handleChatCompletions(c *gin.Context) {
 		return
 	}
 
-	// Select provider based on model name
+	// Strip common prefixes and prepare model ID
-	providerName := "openai" // default
-	modelLower := strings.ToLower(req.Model)
-	if strings.HasPrefix(modelLower, "gemini/") || strings.Contains(modelLower, "gemini") || strings.HasPrefix(modelLower, "google/") {
-		providerName = "gemini"
-	} else if strings.HasPrefix(modelLower, "deepseek/") || (strings.Contains(modelLower, "deepseek") && !strings.Contains(modelLower, "ollama")) {
-		// Only use deepseek provider if it's not explicitly tagged for ollama
-		providerName = "deepseek"
-	} else if strings.HasPrefix(modelLower, "moonshot/") || strings.Contains(modelLower, "kimi") || strings.Contains(modelLower, "moonshot") {
-		providerName = "moonshot"
-	} else if strings.HasPrefix(modelLower, "grok/") || strings.Contains(modelLower, "grok") {
-		providerName = "grok"
-	} else if strings.HasPrefix(modelLower, "ollama/") ||
-		strings.Contains(modelLower, "glm-") ||
-		strings.Contains(modelLower, "qwen") ||
-		strings.Contains(modelLower, "gemma") ||
-		strings.Contains(modelLower, "llama") ||
-		strings.Contains(modelLower, "mistral") ||
-		strings.Contains(modelLower, "phi") ||
-		strings.Contains(modelLower, "yi") ||
-		strings.Contains(modelLower, "codellama") ||
-		strings.Contains(modelLower, "command-r") {
-		providerName = "ollama"
-	}
-
-	provider, ok := s.providers[providerName]
-	if !ok {
-		c.JSON(http.StatusInternalServerError, gin.H{"error": fmt.Sprintf("Provider %s not enabled or supported", providerName)})
-		return
-	}
-
-	// Strip common prefixes
 	modelID := req.Model
 	prefixes := []string{"gemini/", "google/", "openai/", "deepseek/", "moonshot/", "grok/", "ollama/"}
 	for _, p := range prefixes {
@@ -590,6 +559,13 @@ func (s *Server) handleChatCompletions(c *gin.Context) {
 		log.Printf("[ROUTER] %s (%s: %s)", modelID, decision.Strategy, decision.Reason)
 	}
 
+	// Select provider based on the resolved model name
+	provider, providerName, err := s.selectProvider(modelID)
+	if err != nil {
+		c.JSON(http.StatusInternalServerError, gin.H{"error": err.Error()})
+		return
+	}
+
 	// Convert ChatCompletionRequest to UnifiedRequest
 	unifiedReq := &models.UnifiedRequest{
 		Model:            modelID,