feat(config): add support for model prefixes and prefix normalization

Refactor model management to include an optional `prefix` field for model credentials, enabling better namespace handling. Update affected configuration files, APIs, and handlers to support prefix normalization and routing. Remove unused OpenAI compatibility provider logic to simplify processing.

sdk/cliproxy/service.go

@@ -787,7 +787,7 @@ func (s *Service) registerModelsForAuth(a *coreauth.Auth) {
 						if providerKey == "" {
 							providerKey = "openai-compatibility"
 						}
-						GlobalModelRegistry().RegisterClient(a.ID, providerKey, ms)
+						GlobalModelRegistry().RegisterClient(a.ID, providerKey, applyModelPrefixes(ms, a.Prefix, s.cfg.ForceModelPrefix))
 					} else {
 						// Ensure stale registrations are cleared when model list becomes empty.
 						GlobalModelRegistry().UnregisterClient(a.ID)
@@ -807,7 +807,7 @@ func (s *Service) registerModelsForAuth(a *coreauth.Auth) {
 		if key == "" {
 			key = strings.ToLower(strings.TrimSpace(a.Provider))
 		}
-		GlobalModelRegistry().RegisterClient(a.ID, key, models)
+		GlobalModelRegistry().RegisterClient(a.ID, key, applyModelPrefixes(models, a.Prefix, s.cfg != nil && s.cfg.ForceModelPrefix))
 		return
 	}
 
@@ -987,6 +987,48 @@ func applyExcludedModels(models []*ModelInfo, excluded []string) []*ModelInfo {
 	return filtered
 }
 
+func applyModelPrefixes(models []*ModelInfo, prefix string, forceModelPrefix bool) []*ModelInfo {
+	trimmedPrefix := strings.TrimSpace(prefix)
+	if trimmedPrefix == "" || len(models) == 0 {
+		return models
+	}
+
+	out := make([]*ModelInfo, 0, len(models)*2)
+	seen := make(map[string]struct{}, len(models)*2)
+
+	addModel := func(model *ModelInfo) {
+		if model == nil {
+			return
+		}
+		id := strings.TrimSpace(model.ID)
+		if id == "" {
+			return
+		}
+		if _, exists := seen[id]; exists {
+			return
+		}
+		seen[id] = struct{}{}
+		out = append(out, model)
+	}
+
+	for _, model := range models {
+		if model == nil {
+			continue
+		}
+		baseID := strings.TrimSpace(model.ID)
+		if baseID == "" {
+			continue
+		}
+		if !forceModelPrefix || trimmedPrefix == baseID {
+			addModel(model)
+		}
+		clone := *model
+		clone.ID = trimmedPrefix + "/" + baseID
+		addModel(&clone)
+	}
+	return out
+}
+
 // matchWildcard performs case-insensitive wildcard matching where '*' matches any substring.
 func matchWildcard(pattern, value string) bool {
 	if pattern == "" {