Update tree guides

Author: darrenburns

src/textual/widgets/_radio_set.py

@@ -63,6 +63,7 @@ class RadioSet(VerticalScroll, can_focus=True, can_focus_children=False):
             * ToggleButton. If those styles ever get updated, these should be too.
             */
             border: tall $border;
+            background-tint: $foreground 5%;
 
             & > RadioButton.-selected {
                 color: $text;

src/textual/widgets/_tree.py

@@ -628,10 +628,10 @@ class Tree(Generic[TreeDataType], ScrollView, can_focus=True):
                 color: $surface-darken-1;
             }
             & > .tree--guides-hover {
-                color: $surface-darken-2;
+                color: $highlight-cursor;
             }
             & > .tree--guides-selected {
-                color: $surface-darken-2;
+                color: $highlight-cursor;
             }
         }