[BUGFIX] Fix #591: Rename test fixture User/ to Editor/ to match code template toctree

The previous commit changed the toctree entry from User/Index to Editor/Index
but did not rename the corresponding test fixture directory, causing a mismatch.

Co-Authored-By: Claude Opus 4.6 (1M context) <noreply@anthropic.com>

Author: PKuhlmay

Tests/Fixtures/TestExtensions/test_extension/Documentation.tmpl/Editor/Index.rst

@@ -0,0 +1,50 @@
+.. include:: /Includes.rst.txt
+
+.. _for-editors:
+
+===========
+For Editors
+===========
+
+How to use the extension from the perspective of an editor.
+
+Think of common tasks that an editor is likely to perform:
+
+- How do they complete them?
+- What problems are they likely to encounter?
+- What access do they require?
+- What configuration options are available to them?
+
+One example could be adding a frontend plugin to a page and then configuring it.
+
+Language should be non-technical, aim to avoid using acronyms where possible.
+
+Be mindful that editors typically don't have administrative access to the installation.
+
+.. tip::
+
+   Take a break from time to time.
+
+Admonitions should be used to warn the users about potential pitfalls.
+Attract their attention to important elements,
+or add some notes for for information (further reading, for example).
+
+Do not overuse admonitions like notes, important, etc.!
+
+Provide screenshots as needed for making things clear.
+When creating screenshots, try using the Official Introduction Package.
+
+.. figure:: ../Images/UserManual/BackendView.png
+   :class: with-shadow
+   :alt: Backend view
+
+   Default Backend view (caption of the image)
+
+Do not use huge full-screen images, unless it is necessary and serves a good purpose.
+
+.. _editor-faq:
+
+FAQ
+===
+
+Possible subsection: FAQ