SAN FRANCISCO — Dogs outnumber children here, making already assertive dog owners an even more formidable political force. But the emergence in recent years of coyotes in the city’s parks, and sometimes in its expensive backyards and picturesque streets, has raised doubts about whether that founding legacy can survive. Will the two animal worlds — the domesticated and the wild — be able to coexist? Might they even, as many in this liberal city hope, ultimately complement each other? Taking no chances, city officials recently cordoned off trails and barricaded a restroom in an area of Golden Gate Park where...