exit mode in meta levels prior to returning to ground

Formerly I think with hydra we were implicitly exiting. With lithium,
global modes like Buffer remain active even when the original buffer
is killed, so we need to explicitly exit at the appropriate time.

rigpa-mode-mode.el

@@ -360,6 +360,7 @@ current editing tower."
   (let ((ref-buf (rigpa--get-ground-buffer)))
     (rigpa--revert-ui)
     (rigpa--remove-meta-side-effects)
+    (chimera--exit-mode (rigpa-current-mode))
     (when (eq (with-current-buffer ref-buf
                 (rigpa--get-ground-buffer))
               ref-buf)

rigpa-tower-mode.el

@@ -236,6 +236,7 @@ initial editing tower."
       (setq rigpa--last-tower-index rigpa--tower-index-on-entry))
     (rigpa--revert-ui)
     (rigpa--remove-meta-tower-side-effects)
+    (chimera--exit-mode (rigpa-current-mode))
     (kill-matching-buffers (concat "^" rigpa-buffer-prefix) nil t)
     (switch-to-buffer ref-buf)))