Add default collection and document model settings in Config struct

- Introduced default values for CollectionModel and DocumentModel in the Config struct to ensure proper initialization.
- Updated UnmarshalJSON method to set these defaults if not explicitly configured, enhancing the robustness of the configuration handling.

kb/types/config.go

@@ -323,6 +323,16 @@ func (c *Config) UnmarshalJSON(data []byte) error {
 		c.Uploader = "__yao.attachment"
 	}
 
+	// Set default collection model if not configured
+	if c.CollectionModel == "" {
+		c.CollectionModel = "__yao.kb.collection"
+	}
+
+	// Set default document model if not configured
+	if c.DocumentModel == "" {
+		c.DocumentModel = "__yao.kb.document"
+	}
+
 	// Note: Features will be computed later after providers are loaded
 	return nil
 }

kb/types/types.go

@@ -63,6 +63,12 @@ type Config struct {
 	// KV store name (Optional with default value)
 	Store string `json:"store,omitempty" yaml:"store,omitempty"` // Default: "__yao.kb.store"
 
+	// Bind Collection Model
+	CollectionModel string `json:"collection_model,omitempty" yaml:"collection_model,omitempty"` // Default: "__yao.kb.collection"
+
+	// Bind Document Model
+	DocumentModel string `json:"document_model,omitempty" yaml:"document_model,omitempty"` // Default: "__yao.kb.document"
+
 	// PDF parser configuration (Optional)
 	PDF *PDFConfig `json:"pdf,omitempty" yaml:"pdf,omitempty"`