Tooltips in the Notebooks chooser

From the development repository at e819bc4.

Co-Authored-By: Claude Fable 5.1 <noreply@anthropic.com>

client/js/tooltip.js

@@ -50,6 +50,10 @@ function show(element) {
     tooltip.setAttribute('role', 'tooltip');
     document.body.append(tooltip);
   }
+  // A modal dialog is above everything in the body, its tooltips included,
+  // so a tooltip for an element in one lives in the dialog.
+  const home = element.closest('dialog[open]') ?? document.body;
+  if (tooltip.parentElement !== home) home.append(tooltip);
   tooltip.textContent = element.getAttribute('data-help');
   tooltip.hidden = false;
   shownFor = element;