Merge remote-tracking branch 'origin/main' into sq688-sqliimport-help-2

Merge remote-tracking branch 'origin/main' into worktree-agent-afd8071db25362047

Updated: The 6.0.15 changelog lists pull requests #298, #299 and #300 and the work on top

Updated: The admin4 class edit page script runs on plain JavaScript

As #300 did for the other small page scripts: the class edit page focuses
the error list or the attribute changed last, moves attributes in place and
puts back a move the server did not store, without jQuery. The move is
posted with fetch and carries the form token, the CSRF header and
X-Requested-With as before; a click on a move button that is not in an
attribute row does nothing instead of moving another row.

The no-jQuery test lists the class edit and the multi-edit scripts too.

Fixed: No script of the admin designs or the shipped extensions uses an API jQuery 4 removed or deprecated

The online editor's link dialog focuses its first text field with .first()
instead of the jQuery-only :first selector, and TinyMCE's jQuery adapter
binds and unbinds with .on() and .off() instead of the deprecated .bind()
and .unbind().

A new DB-less design test reads every script of design/admin, admin3,
admin4, admin4l and standard, the script elements of their templates, and
those of the extensions the kernel ships, and fails on the statics jQuery 4
removed (jQuery.trim, isArray, type, isFunction ...), on .size(), .andSelf(),
.live() and the .load(fn) shorthand, on the deprecated event binders, and on
jQuery-only positional selectors. Vendored libraries are skipped.

Updated: The 7x SQLI Import help covers the import editor and is a manual of its own

The help gains a page on the import editor in English and German, the other
pages describe spreadsheets, schedules, undo and the conflict rules, and the
help folder is listed in the shipped manuals so it is built with the others.

Fixed: The content edit groups tell screen readers whether they are open, and their names are washed

The plain JavaScript of the content edit page (#300) sets aria-expanded on
the link that opens and closes an attribute group, as it opens, closes or is
opened by a link to one of its attributes. The group's name is washed in
admin4 and in the classic admin, as the class pages already do.

The node details page checks the button's disabled property instead of its
attribute's value, which is empty for a bare disabled attribute.