Object: Hide Unselected Artwork keeps a selected layer's art and groups that hold locked guides

With a layer selected, Object > Hide > Unselected Artwork hid every object
on that layer, since the selected layer was dropped from the objects to
keep. The objects of a selected layer now count as selected.

While Lock Guides is on, a group that held a guide path was hidden whole,
which hid the guide with it. Guide paths now count as selected, so the
command keeps such a group visible and hides its other members one by one.

docs/mcp.md

@@ -1372,8 +1372,8 @@ is one of them, and `edit.undo` selects them again with the key object.
 `object.hide.unselected` (Object › Hide › Unselected Artwork, Cmd+Alt+Shift+3) hides, in one undo step, every
 object that `select.all` takes and that is neither selected nor holds a selected object, and returns `{count}`. In a
 group that holds a selected object it hides the group's other members one by one; a clip group, a compound path or
-another object that holds a selected object stays as it is with its members. While Lock Guides is on it leaves the
-guide paths as they are. The selection stays as it is, and `object.showAll` shows the objects again. With nothing to
+another object that holds a selected object stays as it is with its members. The objects of a selected layer count as
+selected. While Lock Guides is on, the guide paths count as selected and stay as they are. The selection stays as it is, and `object.showAll` shows the objects again. With nothing to
 hide it records no undo step. In isolation mode the menu item is disabled, and the command returns the error "exit
 isolation mode first" and changes nothing.