sipario 0.4.0

• Added: sipario export pdf and sipario export pptx. The deck as
  a PDF, a page per step at the stage's size, and as a PowerPoint deck of
  a picture per step with the step's script in its notes. Both photograph
  the new /print page through a browser already on the machine (Chrome,
  Chromium, Brave or Edge; SIPARIO_BROWSER names one elsewhere), so
  neither can disagree with the room. It refuses rather than writing a
  file that is wrong only to look at: a step the talk's sheets hide, a
  PDF a page short, a figure that did not load, and a save landing
  mid-run, which would pair one draft's pictures with another's scripts.
  A browser that goes away mid-run is an error too, rather than a wait
  that never ends.
  exportPdf, exportPptx, outline, printPage and findBrowser
  join the library's surface.
• Fixed: printing the deck page from the browser stacked every slide
  on one sheet. The rule that tried is gone; /print is the page that
  prints.
• Fixed: a request the URL parser refuses, such as GET //[/, took
  the server down. It threw where nothing could catch it, so anyone able
  to reach the port could end a talk between two slides. Such a request
  is now answered 400 and the server stays up.
• Fixed: renumber counted a # line inside a comment at the head
  of a deck as a movement. The renderer ignores that comment, so a deck
  that rendered correctly was renumbered wrongly from its second slide
  on, and a number-from: line below the comment was never read at all.
  Both now skip the comment, which is put back untouched.
• Fixed: renumber prefixed a quoted id rather than reading through
  the quotes, so id: '1-example' became id: 1-'1-example' — a
  different anchor, and every link to that slide broken.
• Fixed: a link to a slide whose id is not plain ASCII opened the
  wrong slide. #2-café travels as #2-caf%C3%A9, which matched no id,
  so the deck opened at the start and then rewrote the address bar,
  losing the link. The fragment is now decoded before it is matched, and
  encoded when the deck writes it, so an id holding what looks like an
  escape — 2-100%20 — is read back as the name it is rather than as
  2-100 .
• Fixed: the presenter window called itself live before any deck had
  answered it. The page paints itself on load and the paint was what
  marked it live, so a /presenter opened with no deck behind it sat
  showing the first slide's script instead of the warning that the deck
  is not answering. Only a message from a deck marks it live now.
• Changed: the server closes its file watchers when it closes, and
  asked for port 0 names the port it was actually given.