v0.5.8 — the Editor is the whole window

• Nothing is drawn above the Editor any more — no KPI rail, no header, no
  tab bar. It was a card on a canvas while also being the only view that wants
  the entire screen, and the cost was visible: a rounded top edge under a bar
  with nothing above it, 24px of canvas down both flanks of a file tree, and a
  bottom edge that read as a scroll that was not there. Padding zero, radius
  zero, no outer border: the panel IS the window. It had shrunk to a small bar
  before, and a small bar is still a lid.
• One thin bar inside the page carries the way out, which tree is open and
  what the door said about it. It sits outside the panel deliberately: the
  refusal and the loading states replace the panel whole, and the exit must not
  go with it. The exit is an arrow — a glyph in a bar of monospace facts, with
  its words in aria-label and title so nothing is lost to a reader who
  cannot see it — and onBack is REQUIRED by the page's props, because this is
  the one view with no tab bar and a caller must not be able to strand somebody
  on it by omission.
• Header.compact is deleted: a second shape of that component nothing
  could reach any more, still asking to be kept in step.
• Four assertions pin the new geometry and each was measured red at its own
  site. One of them was born FALSE and is fixed here — it read the style
  attribute with the pattern's attribute order backwards, matched nothing, and
  undefined !== true passed with the padding put straight back. It now has to
  FIND the node before it says anything about it, and that blind spot is
  mutated red too.