export() resized the canvas, changed its scale and offset, and only
restored them after the blob came back. Anything that threw in between —
most plausibly toBlob on a workflow large enough to exceed the browser's
canvas limit, which is exactly the workflow someone wants a PNG of — left
the user's view stuck at export dimensions until they reloaded.
restoreState() now runs in a finally, followed by a redraw.
The GuLuLu yes/no callbacks also swallowed the rejection, so the failure
looked like the button simply doing nothing. They now go through a wrapper
that logs and shows a toast naming the canvas limit as the likely cause.
kk8bit
75b1dde389