Allow selection of PCB_MARKERs when not on active layer

Fixes https://gitlab.com/kicad/code/kicad/-/issues/19258

patch

@@ -0,0 +1,13 @@
+diff --git a/pcbnew/tools/pcb_selection_tool.cpp b/pcbnew/tools/pcb_selection_tool.cpp
+index 34144c325d..6d4b64bdb5 100644
+--- a/pcbnew/tools/pcb_selection_tool.cpp
++++ b/pcbnew/tools/pcb_selection_tool.cpp
+@@ -2837,7 +2837,7 @@ bool PCB_SELECTION_TOOL::Selectable( const BOARD_ITEM* aItem, bool checkVisibili
+             }
+         }
+ 
+-        if( !onActiveLayer ) // We do not want to select items that are in the background
++        if( !onActiveLayer && aItem->Type() != PCB_MARKER_T ) // We do not want to select items that are in the background
+             return false;
+     }
+ 

pcbnew/tools/pcb_selection_tool.cpp

@@ -2837,8 +2837,11 @@ bool PCB_SELECTION_TOOL::Selectable( const BOARD_ITEM* aItem, bool checkVisibili
             }
         }
 
-        if( !onActiveLayer ) // We do not want to select items that are in the background
+        if( !onActiveLayer && aItem->Type() != PCB_MARKER_T )
+        {
+            // We do not want to select items that are in the background
             return false;
+        }
     }
 
     if( aItem->Type() == PCB_FOOTPRINT_T )