The loop that drives `scope.reconcile` was marked as running until the
promise of its last run had settled, which is a few microtasks after the
loop itself had checked for new values. A value arriving in that window
found the loop "running", was left to it, and was never processed: a
connection appearing at that moment would never get its publisher.
The flag is now cleared the moment the loop ends, so such a value starts
a new loop. The regression test drives the window microtask by microtask.