Set x-robots-tag for preview requests

CHANGELOG.md

@@ -2,6 +2,7 @@
 
 ## Unreleased
 
+- Craft now sends `X-Robots-Tag: none` headers for preview requests. ([#15612](https://github.com/craftcms/cms/pull/15612), [#15586](https://github.com/craftcms/cms/issues/15586))
 - Fixed a SQL error that occurred when running the `db/convert-charset` command if there were any custom database views or sequences. ([#15598](https://github.com/craftcms/cms/issues/15598))
 - Fixed a bug where `craft\helpers\Db::supportsTimeZones()` could return `false` on databases that supported time zone conversion. ([#15592](https://github.com/craftcms/cms/issues/15592))
 - Fixed a bug where Assets fields were validating settings that weren’t applicable depending on the “Restrict assets to a single location” setting. ([#15545](https://github.com/craftcms/cms/issues/15545))

src/web/Application.php

@@ -191,6 +191,7 @@ public function handleRequest($request, bool $skipSpecialHandling = false): Base
                 $generalConfig->disallowRobots ||
                 $request->getIsCpRequest() ||
                 $request->getToken() !== null ||
+                $request->getIsPreview() ||
                 ($request->getIsActionRequest() && !($request->getIsLoginRequest() && $request->getIsGet()))
             ) {
                 $headers->set('X-Robots-Tag', 'none');