Refactor sud JSON pot params under a nested 'pot' key

Top-level pot_mass/pot_material/L/Td/grain_mass/water_mass and their
per-step overrides are now grouped under a 'pot' sub-object, matching
the structure already applied to sud_0010.json's parent level. Updated
all sude/*.json files and the parsing/consuming code in components/sud.py,
tasks/sud.py, components/sud_forecast.py, and scripts/demos/sud/demo_sud.py.

Co-Authored-By: Claude Sonnet 4.6 <noreply@anthropic.com>
Claude-Session: https://claude.ai/code/session_01T52JH848ojhXXHn1bAzdC3

scripts/demos/sud/demo_sud.py

@@ -42,7 +42,8 @@ if __name__ == '__main__':
 		sud.load(json.load(f))
 
 	first_step = sud.schedule[0]
-	plant_params = sud.derive_plant_params(first_step['grain_mass'], first_step['water_mass'])
+	first_pot = first_step.get('pot', {})
+	plant_params = sud.derive_plant_params(first_pot.get('grain_mass', 0), first_pot.get('water_mass', 0))
 
 	ctrl = TempController(dt)
 	ctrl.set_params(ctrl_params)
@@ -74,7 +75,8 @@ if __name__ == '__main__':
 		stirrer.set_speed(speed)
 
 	def apply_plant_params(step):
-		params = sud.derive_plant_params(step['grain_mass'], step['water_mass'])
+		pot = step.get('pot', {})
+		params = sud.derive_plant_params(pot.get('grain_mass', 0), pot.get('water_mass', 0))
 		plant.set_plant_params(params)
 		ctrl.set_model_plant_params(params)