Boiled-off liquid particles stay in the solver and can block a heater

What. When a liquid particle boils off, the heat plug-in stops exchanging heat with it, but the particle stays in the liquid solver with its mass and position. A boiled-off layer on a heater holds the remaining liquid off the heater, so heating stops.

Number. Water at 99 °C on a 177 °C plate: heating stops once the bottom layer, 25 % of the mass, has boiled off. The rest stays at 99.05 °C.

Why. The liquid solver has no public call yet to remove particles during a run.

Workaround. Read evaporated_in_solver from the plug-in. It counts the boiled-off particles that are still in the solver, and a run that boils must check it is 0. Keep boiling scenes short of boil-off, or heat with power_density (volumetric, needs no contact).

Planned fix. The plug-in will retire boiled-off particles once the liquid solver has a retire call; it is in progress.