{{/*
  Anchor id for a section: its own `id`, else one made from its `toc`,
  `kicker`, or `headline`. Shared by the section wrapper and the rail's
  "On this page" index so the two always agree.
*/}}
{{ $id := "" }}
{{ with .id }}
  {{ $id = . }}
{{ else }}
  {{ with (or .toc .kicker .headline) }}{{ $id = . | plainify | anchorize }}{{ end }}
{{ end }}
{{ return $id }}