Remove OpenAI API references from Assistant struct and initialization

- Eliminate the `openai` field from the `Assistant` struct and its initialization in the `initialize` method, streamlining the Assistant's internal structure.
- This change simplifies the codebase by removing unnecessary dependencies on the OpenAI API, enhancing maintainability.

agent/assistant/assistant.go

@@ -215,7 +215,6 @@ func (ast *Assistant) Clone() *Assistant {
 			UpdatedAt:            ast.UpdatedAt,
 		},
 		HookScript: ast.HookScript,
-		openai:     ast.openai,
 	}
 
 	// Deep copy tags

agent/assistant/load.go

@@ -15,7 +15,6 @@ import (
 	"github.com/yaoapp/yao/agent/i18n"
 	searchTypes "github.com/yaoapp/yao/agent/search/types"
 	store "github.com/yaoapp/yao/agent/store/types"
-	"github.com/yaoapp/yao/openai"
 	"gopkg.in/yaml.v3"
 )
 
@@ -796,12 +795,6 @@ func (ast *Assistant) initialize() error {
 	}
 	ast.Connector = conn
 
-	api, err := openai.New(conn)
-	if err != nil {
-		return err
-	}
-	ast.openai = api
-
 	// Register scripts as process handlers
 	if len(ast.Scripts) > 0 {
 		if err := ast.RegisterScripts(); err != nil {

agent/assistant/types.go

@@ -8,7 +8,6 @@ import (
 
 	outputMessage "github.com/yaoapp/yao/agent/output/message"
 	store "github.com/yaoapp/yao/agent/store/types"
-	api "github.com/yaoapp/yao/openai"
 )
 
 const (
@@ -34,8 +33,7 @@ type Assistant struct {
 
 	// Internal
 	// ===============================
-	openai *api.OpenAI // OpenAI API
+	vision bool // Whether this assistant supports vision
-	vision bool        // Whether this assistant supports vision
 }
 
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