v2.2.6 — Abilities starts closed

Changed

• Abilities in the sidebar starts closed, and opens only when you click it. It opened by
  default, and it also reopened itself whenever the active page was one of its two members — so a
  visit to Skills undid the collapse. Both are gone: absent means closed, and the heading is the
  only thing that opens it. Infrastructure already started closed and keeps its own reopen
  behaviour, which was not part of the ask.
  (#253)
• Both rail groups remember whether you closed them. They held that in local state, so the choice
  lasted until the next reload — and the comment on that state called collapsing "the operator's
  choice, not the default", which a choice that does not survive a reload is not. They now use
  collapsed_groups, the map the sidebar already round-trips for chat project groups, under
  nav:-prefixed keys so they cannot collide with a project of the same name.
  (#253)