Be more pedantic about RECURSE_MODE.

Also fixes an invalid iterator bug.

Also adds mirroring support for PCB_GROUPs.

Fixes https://gitlab.com/kicad/code/kicad/-/issues/21107

common/commit.cpp

@@ -63,7 +63,7 @@ COMMIT& COMMIT::Stage( EDA_ITEM* aItem, CHANGE_TYPE aChangeType, BASE_SCREEN* aS
         makeEntry( aItem, CHT_REMOVE | flag, makeImage( aItem ), aScreen );
 
         if( EDA_GROUP* parentGroup = aItem->GetParentGroup() )
-            Modify( parentGroup->AsEdaItem(), aScreen );
+            Modify( parentGroup->AsEdaItem(), aScreen, RECURSE_MODE::NO_RECURSE );
 
         break;