Update SOILWAT2 interface

- update to SOILWAT2 branch release/devel_v8.4.0 commit 8262b29eaf50ab7df1d9b536b31cab9519a14ff5 (2026-Jan-16)
* struct SW_DOMAIN gained attribute isSimDomDiscrete (replacing DomainType)

Author: dschlaep

src/rSW_Domain.c

@@ -62,7 +62,7 @@ void onSet_SW_DOM(SEXP InputData, LOG_INFO* LogInfo) {
     // copy here complete and correct values into `SoilWatDomain`
 
     // Currently not implemented in rSOILWAT2 but required in SOILWAT2
-    strcpy(SoilWatDomain.DomainType, "s");
+    SoilWatDomain.isSimDomDiscrete = swTRUE;
     SoilWatDomain.nDimX = 1;
     SoilWatDomain.nDimY = 1;
     SoilWatDomain.nDimS = 1;