test(timeout): assert real setsid/setpgid call sites in the #1003 tty guard

The guard used `! grep`, which bats never treats as a failure (SC2314) and
which also tripped the test-script lint step. Even made real, a plain grep
for setsid would false-positive on the comments that explain why it is
avoided. Anchor the match to call statements at line start so the regression
guard actually verifies the perl fallback uses setpgid, not setsid.