44e15ea1b7
An operator argv runs via `sh -c`, so ["ls","&&","rm","-rf","/"] passed an
argv[0]-only allowlist check with {ls} then executed rm. Now every command
position (argv[0] + the token after each &&/||/|/;/& separator) must be
allowlisted; shell builtins are implicit, redirect targets are treated as
filenames. Tests for the bypass, an all-allowed chain, and a redirect target.