PotTask.on_process() only calls Pot.process() once Pot.is_configured()
- which required plant params (M/C/L/Td) that, by design, only ever
came from a Sud's own doc via SudTask.apply_plant_params(). So with no
Sud loaded (or the temp controller disabled), the simulated Pot just
sat inert: manually driving the heater never moved its temperature at
all.
EMPTY_SUD's pot_mass/pot_material defaulted to 0/None, which would
have made a zero-mass plant (a ZeroDivisionError in Pot.process()) -
they're actually the physical kettle's own properties, not really
per-recipe (every sude/*.json so far uses the same pot), so default
them to that real kettle's values instead. server/brewpi.py now seeds
the Pot with derive_plant_params() from the not-yet-loaded Sud right
away, same as ambient temperature already was - a real Sud's own doc
still overrides these the moment one is loaded.