refactor(auth): Centralize logging for saving credentials

The logic for logging the path where credentials are saved was duplicated across several client implementations.

This commit refactors this behavior by creating a new centralized function, `misc.LogSavingCredentials`, to handle this logging. The `SaveTokenToFile` method in each authentication token storage struct now calls this new function, ensuring consistent logging and reducing code duplication.

The redundant logging statements in the client-level `SaveTokenToFile` methods have been removed.

internal/client/gemini-cli_client.go

@@ -831,7 +831,6 @@ func (c *GeminiCLIClient) GetProjectList(ctx context.Context) (*interfaces.GCPPr
 //   - error: An error if the save operation fails, nil otherwise.
 func (c *GeminiCLIClient) SaveTokenToFile() error {
 	fileName := filepath.Join(c.cfg.AuthDir, fmt.Sprintf("%s-%s.json", c.tokenStorage.(*geminiAuth.GeminiTokenStorage).Email, c.tokenStorage.(*geminiAuth.GeminiTokenStorage).ProjectID))
-	log.Infof("Saving credentials to %s", fileName)
 	return c.tokenStorage.SaveTokenToFile(fileName)
 }
 

internal/client/gemini-web_client.go

@@ -842,7 +842,6 @@ func (c *GeminiWebClient) SaveTokenToFile() error {
 		}
 		return ts.SaveTokenToFile(c.tokenFilePath)
 	}
-	log.Debugf("Saving Gemini Web cookie snapshot to %s", filepath.Base(util.CookieSnapshotPath(c.tokenFilePath)))
 	return c.snapshotManager.Persist()
 }