An index is the skim layer: its entries decide whether a reader opens the page, so an entry
that runs 250 characters is a paragraph wearing a bullet. Four entries in `tools/index.md`
(`dotfiles-deploy`, `packages`, `pcie-probe`, `remote-job`) now say what the page is for in one
line and let the page carry the detail — which is the whole argument for progressive disclosure
having an index at all.
`engineering/infra/index.md` pointed at `../sdlc.md` with no description at all; it now carries
the one from that page's frontmatter, like its four siblings.
Refs #64
Frank
c37ad6e870