The composable interpreter treated a step as done after a 60 ms gap
with no commits, and treated its 2 s timeout as done too. Slow sync or
reflow work could finish after the step, so a case could assert on a
half-synced file.
Each event step now waits, as the plugin waitForLayoutUpdate does,
until every pending work tracked by the reflow registry has drained:
the watcher's sync wait, the sync it starts, and layout and text
reflow. A step that does not drain within 2 s fails the test and names
the work still pending, and the next variant starts with nothing
pending.
The tests cover an edit with a deliberately slow sync, undo and redo
steps that must wait for the watcher's touch-component, translation
and derived commits, a sync that never finishes, and a restart of the
edit watchers, which must keep the undo entries of an edit the same.