Issues with version-switcher and dirhtml builder

[cgohlke]

Re #1795

Hello,

using Sphinx 8.0.2 with pydata-sphinx-theme 0.15.4 (or 0.16.0rc0), I am trying to get the version-switcher working with the dirhtml builder and ran into two issues:

1. Page names like api/index (DOCUMENTATION_OPTIONS.pagename = 'api/index') are mapped to api/index/, not api/
2. Some urls contain double slashes //, as already noted in fix version-switcher with dirhtml builder #1795 (comment)

The following patch works for me, but I haven't formally tested it:

diff --git a/src/pydata_sphinx_theme/assets/scripts/pydata-sphinx-theme.js b/src/pydata_sphinx_theme/assets/scripts/pydata-sphinx-theme.js
index 0c876e6..03a42a2 100644
--- a/src/pydata_sphinx_theme/assets/scripts/pydata-sphinx-theme.js
+++ b/src/pydata_sphinx_theme/assets/scripts/pydata-sphinx-theme.js
@@ -346,8 +346,8 @@ var setupSearchButtons = () => {
  */
 var getCurrentUrlPath = () => {
   if (DOCUMENTATION_OPTIONS.BUILDER == "dirhtml") {
-    return DOCUMENTATION_OPTIONS.pagename == "index"
-      ? `/`
+    return DOCUMENTATION_OPTIONS.pagename.endsWith("index")
+      ? `${DOCUMENTATION_OPTIONS.pagename.substring(0, DOCUMENTATION_OPTIONS.pagename.length - 5)}`
       : `${DOCUMENTATION_OPTIONS.pagename}/`;
   }
   return `${DOCUMENTATION_OPTIONS.pagename}.html`;

Does this look correct?