fix: use Printf instead of Println for formatted output

Line 101: fmt.Println with %d directive changed to fmt.Printf.
Println doesn't interpret format directives; Printf required for %d.

Fixes go vet error.

cmd/workflow-runner/main.go

@@ -98,7 +98,7 @@ func main() {
 	fmt.Println(sep)
 
 	// Execution history explanation
-	fmt.Println("\n📜 EXECUTION HISTORY (%d events)")
+	fmt.Printf("\n📜 EXECUTION HISTORY (%d events)\n", descResp.WorkflowExecutionInfo.HistoryLength)
 	fmt.Println(sep)
 	
 	historyLength := descResp.WorkflowExecutionInfo.HistoryLength