feat: open floating explorer as Tree in Insert mode

src/ruby_host.rb

@@ -53,7 +53,7 @@ module Vamp
       @bindings = []
       @leader = "space"
       @file_explorer_side = "right"
-      @file_picker_view = "list"
+      @file_picker_view = "tree"
       @file_explorer_view = "tree"
     end