refactor(auth): simplify file handling logic and remove redundant comparison functions

feat(auth): fetch and update Antigravity project ID from metadata during filestore operations

- Added support to retrieve and update `project_id` using the access token if missing in metadata.
- Integrated HTTP client to fetch project ID dynamically.
- Enhanced metadata persistence logic.

internal/runtime/executor/antigravity_executor.go

@@ -25,6 +25,7 @@ import (
 	"github.com/router-for-me/CLIProxyAPI/v6/internal/config"
 	"github.com/router-for-me/CLIProxyAPI/v6/internal/registry"
 	"github.com/router-for-me/CLIProxyAPI/v6/internal/util"
+	sdkAuth "github.com/router-for-me/CLIProxyAPI/v6/sdk/auth"
 	cliproxyauth "github.com/router-for-me/CLIProxyAPI/v6/sdk/cliproxy/auth"
 	cliproxyexecutor "github.com/router-for-me/CLIProxyAPI/v6/sdk/cliproxy/executor"
 	sdktranslator "github.com/router-for-me/CLIProxyAPI/v6/sdk/translator"
@@ -1104,12 +1105,49 @@ func (e *AntigravityExecutor) refreshToken(ctx context.Context, auth *cliproxyau
 		auth.Metadata["refresh_token"] = tokenResp.RefreshToken
 	}
 	auth.Metadata["expires_in"] = tokenResp.ExpiresIn
-	auth.Metadata["timestamp"] = time.Now().UnixMilli()
-	auth.Metadata["expired"] = time.Now().Add(time.Duration(tokenResp.ExpiresIn) * time.Second).Format(time.RFC3339)
+	now := time.Now()
+	auth.Metadata["timestamp"] = now.UnixMilli()
+	auth.Metadata["expired"] = now.Add(time.Duration(tokenResp.ExpiresIn) * time.Second).Format(time.RFC3339)
 	auth.Metadata["type"] = antigravityAuthType
+	if errProject := e.ensureAntigravityProjectID(ctx, auth, tokenResp.AccessToken); errProject != nil {
+		log.Warnf("antigravity executor: ensure project id failed: %v", errProject)
+	}
 	return auth, nil
 }
 
+func (e *AntigravityExecutor) ensureAntigravityProjectID(ctx context.Context, auth *cliproxyauth.Auth, accessToken string) error {
+	if auth == nil {
+		return nil
+	}
+
+	if auth.Metadata["project_id"] != nil {
+		return nil
+	}
+
+	token := strings.TrimSpace(accessToken)
+	if token == "" {
+		token = metaStringValue(auth.Metadata, "access_token")
+	}
+	if token == "" {
+		return nil
+	}
+
+	httpClient := newProxyAwareHTTPClient(ctx, e.cfg, auth, 0)
+	projectID, errFetch := sdkAuth.FetchAntigravityProjectID(ctx, token, httpClient)
+	if errFetch != nil {
+		return errFetch
+	}
+	if strings.TrimSpace(projectID) == "" {
+		return nil
+	}
+	if auth.Metadata == nil {
+		auth.Metadata = make(map[string]any)
+	}
+	auth.Metadata["project_id"] = strings.TrimSpace(projectID)
+
+	return nil
+}
+
 func (e *AntigravityExecutor) buildRequest(ctx context.Context, auth *cliproxyauth.Auth, token, modelName string, payload []byte, stream bool, alt, baseURL string) (*http.Request, error) {
 	if token == "" {
 		return nil, statusErr{code: http.StatusUnauthorized, msg: "missing access token"}