config: seed plant params from Pot.water_mass at server startup

Sud._parse_data now falls through to pot_config for all hardware keys
(mass, material, L, Td) — EMPTY_SUD no longer shadows them. brewpi.py
seeds pot/tc plant params from Pot.water_mass on startup so the
simulated plant is configured before any sud is loaded.

Co-Authored-By: Claude Sonnet 4.6 <noreply@anthropic.com>

server/brewpi.py

@@ -92,14 +92,6 @@ if __name__ == '__main__':
 	sensor_task = TempSensorTask(sensor, DT_TASK, dispatcher.msgio_get("Sensor"))
 	taskmgr.add(sensor_task)
 
-	# Pot - deliberately left without plant params (M/C/L/Td) here: a
-	# Sud's own doc is the only source for those now (see tasks/sud.py's
-	# SudTask.apply_plant_params(), called immediately on Load), so the
-	# simulated Pot stays inert (Pot.is_configured() is False, PotTask
-	# skips process() - see there) until one actually is loaded (PotReal
-	# just ignores this - see there). Ambient is independent of any Sud
-	# (a global setting, changeable live via the System channel - see
-	# on_system_recv() below), so it's set right away regardless.
 	pot.set_ambient_temperature(theta_amb)
 	taskmgr.add(PotTask(pot, DT_TASK, dispatcher.msgio_get("Pot")))
 
@@ -107,18 +99,22 @@ if __name__ == '__main__':
 	heater_task = HeaterTask(heater, DT_TASK, dispatcher.msgio_get("Heater"))
 	taskmgr.add(heater_task)
 
-	# Temperature Controller - PID gains are server/hardware-level
-	# config, independent of any Sud, so they're set right away; "Normal"
-	# has no internal model/ambient at all (see temp_controller.py vs.
-	# temp_controller_smith.py.), and Smith's model plant params are -
-	# like the real Pot's above - deliberately left unset here, only
-	# ever coming from a Sud's own doc.
 	tc = PidFactory.create(config['TempCtrl']['pid_type'], DT)
 	tc.set_params(config['TempCtrl'])
 	tc.set_ambient_temperature(theta_amb)
 	tc_task = TcTask(tc, DT_TASK, dispatcher.msgio_get("TempCtrl"))
 	taskmgr.add(tc_task)
 
+	# Seed plant params from config so pot/tc are configured before any sud
+	# is loaded - Pot.water_mass in config is how much water is already in
+	# the kettle at startup (e.g. strike water pre-filled). A loaded sud's
+	# own apply_plant_params() will override this on the first step.
+	startup_water = config.get('Pot', {}).get('water_mass', 0)
+	if startup_water > 0:
+		startup_params = sud.derive_plant_params(0, startup_water)
+		pot.set_plant_params(startup_params)
+		tc.set_model_plant_params(startup_params)
+
 	# Stirrer
 	stirrer = StirrerFactory.create(config['Stirrer']['type'], DT, config['Stirrer'])
 	stirrer_task = StirrerTask(stirrer, DT_TASK, dispatcher.msgio_get("Stirrer"))