Issue #3590981 by joshuami: Default editor_instructions help link should open in a new tab.
Add target="_blank" to the anchor in the default editor_instructions config value so fresh installs render the "PDF Accessibility Help" link as a new-tab link. Editors who click the help link from inside the CKEditor "Add or select media" modal no longer lose their upload context to an in-tab navigation.
Existing sites with a customized editor_instructions value are left untouched; release notes will direct operators to add target="_blank" themselves if they want the new-tab behavior.
Co-Authored-By: Claude Opus 4.7 (1M context) noreply@anthropic.com
Closes #3590981