Plot the Sud demo's plant M/C over the run

Adds a third figure tracking plant.M/plant.C alongside the existing
temperature/state plots, making the per-step mass changes (malt going
in, water boiling off) visible.

Co-Authored-By: Claude Sonnet 4.6 <noreply@anthropic.com>
Claude-Session: https://claude.ai/code/session_01CgR9tPaSzFkAwRAUyeaaCD

sude/sud_0010.json

@@ -95,6 +95,7 @@
 			}
 		},
 		{
+			"water_mass"		: 20,
 			"descr": "Heizen Abmaischen",
 			"ramp": {
 				"rate": 1.0,
@@ -102,7 +103,7 @@
 			}
 		},
 		{
-			"water_mass"		: 21,
+			"water_mass"		: 20,
 			"descr": "Halten Abmaischen",
 			"user_message": "Quittieren zum Abmaischen",
 			"user_wait_for_continue": true,