chore(tools): actually record the exec bit on setlist.py + its test

Third time. tools/gig-up.sh's 'tools executable' check (added yesterday for exactly
this) is why it surfaced: setlist.py went into 04fc8c7c with content but mode 100644,
so a fresh clone would get 'permission denied' from a HARD gate check. chmod +x
touches the working tree; git stores the bit separately and needs
`git update-index --chmod=+x`, and even then a pathspec-limited commit can leave
HEAD at 100644 while the index says 100755 — which is what happened here.

Verify with `git ls-tree HEAD <file>`, never `ls -l`.