fix: Fix material decorator wiring in Python Examples (#4110)

Fix naming of material decorator for ITk example. Now, `materialDecorator` is used for `TGeoDetector`. Variable `mdecorator` exists only in `getOpenDataDetector()` function, not used by ITk.


<!-- This is an auto-generated comment: release notes by coderabbit.ai -->

## Summary by CodeRabbit

- **New Features**
  - Expanded detector configuration options for enhanced setup flexibility.
- **Refactor**
  - Updated configuration parameter naming for improved clarity and consistency without altering functionality.

<!-- end of auto-generated comment: release notes by coderabbit.ai -->

Examples/Python/python/acts/examples/itk.py

@@ -59,7 +59,7 @@ def buildITkGeometry(
             surfaceLogLevel=customLogLevel(),
             layerLogLevel=customLogLevel(),
             volumeLogLevel=customLogLevel(),
-            mdecorator=matDeco,
+            materialDecorator=matDeco,
         )
 
     Volume = TGeoDetector.Config.Volume
@@ -85,7 +85,7 @@ def buildITkGeometry(
     # This specification should be kept in sync with `itk-hgtd/tgeo-atlas-itk-hgtd.json`.
     return TGeoDetector(
         fileName=str(tgeo_fileName),
-        mdecorator=matDeco,
+        materialDecorator=matDeco,
         buildBeamPipe=True,
         unitScalor=1.0,  # explicit units
         beamPipeRadius=23.934 * u.mm,

Examples/Python/src/Detector.cpp

@@ -219,6 +219,7 @@ void addDetector(Context& ctx) {
     ACTS_PYTHON_MEMBER(beamPipeEnvelopeR);
     ACTS_PYTHON_MEMBER(layerEnvelopeR);
     ACTS_PYTHON_MEMBER(unitScalor);
+    ACTS_PYTHON_MEMBER(materialDecorator);
     ACTS_PYTHON_MEMBER(volumes);
     ACTS_PYTHON_STRUCT_END();
 

Examples/Scripts/Python/propagation.py

@@ -72,7 +72,7 @@ def runPropagation(trackingGeometry, field, outputDir, s=None, decorators=[]):
     # matDeco = acts.IMaterialDecorator.fromFile("material.root")
 
     ## Generic detector: Default
-    detector = GenericDetector(mdecorator=matDeco)
+    detector = GenericDetector(materialDecorator=matDeco)
 
     ## Alternative: Aligned detector in a couple of modes
     # detector = AlignedDetector(