TextEditCtx::select compared the tap against the laid-out text's own box
and cleared the selection for anything outside it. An empty field lays
out to a zero-width box, so tapping the composer granted focus and opened
the keyboard with no caret, and insert_str returns early without one --
every keystroke went nowhere and no glyph was ever emitted. Parley clamps
a point outside the layout by itself, and a press reaching select() has
already been hit-tested to the widget, so there was nothing for the
'outside' branch to mean.
insert_str now debug_asserts rather than dropping input silently, and
UiRenderState::draw_started -- a re-entrancy guard whose test was written
after its own remove(), so it could never fire, and which grew by one
entry per widget ever drawn -- is restored to what it was meant to be:
inserted around Widget::draw, removed when it returns, asserted empty at
the top of every update.