Archiving back to opener (#1210)

* Move "Back to Opener" explainer to Alumni section, indicating shift to Chromium user-agent feature

* Clarify "Back to Opener" explainer to reflect its status as a Chromium feature

* Remove "Back to Opener" issue template as it is no longer needed

* Update "Back to Opener" explainer to reflect archived status and current Chromium feature pursuit

* Remove participation section from "Back to Opener" explainer as it is no longer relevant

* Correct terminology in "Back to Opener" explainer to specify feature as a Chromium feature

Author: victorhuangwq

.github/ISSUE_TEMPLATE/back-to-opener.md

@@ -6,13 +6,9 @@ Authors: [Victor Huang](https://github.com/victorhuangwq)
 
 This document is intended as a starting point for engaging the community and standards bodies in developing collaborative solutions fit for standardization. As the solutions to problems described in this document progress along the standards-track, we will retain this document as an archive and use this section to keep the community up-to-date with the most current standards venue and content location of future work and discussions.
 
-This document status: Active  
-Expected venue: [WHAT WG](https://whatwg.org/)  
-Current version: this document
-
-## Participate
-
-- [Issue tracker](https://github.com/MicrosoftEdge/MSEdgeExplainers/issues/new?assignees=victorhuangwq&labels=BackToOpener&title=%5BBackToOpener%5D+%3CTITLE+HERE%3E)
+This document status: **Archived**  
+Expected venue: N/A  
+Current version: We are pursuing this feature as a [Chromium feature](https://issues.chromium.org/issues/448173940) instead of a web platform one.
 
 <!-- - [Discussion forum] -->
 

BackToOpener/explainer.md

@@ -111,7 +111,6 @@ These are proposals that are still really early in their lifecycle. We might jus
 | [Animation Smoothness](AnimationSmoothness/explainer.md) | <a href="https://github.com/MicrosoftEdge/MSEdgeExplainers/labels/AnimationSmoothness">![GitHub issues by-label](https://img.shields.io/github/issues/MicrosoftEdge/MSEdgeExplainers/AnimationSmoothness?label=issues)</a> | [New Issue...](https://github.com/MicrosoftEdge/MSEdgeExplainers/issues/new?assignees=jenna-sasson&labels=AnimationSmoothness&title=%5BAnimationSmoothness%5D+%3CTITLE+HERE%3E) | Web Perf |
 | [Event Phases For Reliably Fast DOM Operations](https://github.com/MicrosoftEdge/MSEdgeExplainers/blob/main/EventPhases/explainer.md) | <a href="https://github.com/MicrosoftEdge/MSEdgeExplainers/labels/EventPhases">![GitHub issues by-label](https://img.shields.io/github/issues/MicrosoftEdge/MSEdgeExplainers/EventPhases?label=issues)</a> | [New Issue...](https://github.com/MicrosoftEdge/MSEdgeExplainers/issues/new?assignees=slightlyoff&labels=EventPhases&title=%5BEventPhases%5D+%3CTITLE+HERE%3E) | Web Perf |
 | [Delayed Messages API](https://github.com/MicrosoftEdge/MSEdgeExplainers/blob/main/DelayedMessages/explainer.md) | <a href="https://github.com/MicrosoftEdge/MSEdgeExplainers/labels/DelayedMessages">![GitHub issues by-label](https://img.shields.io/github/issues/MicrosoftEdge/MSEdgeExplainers/DelayedMessages?label=issues)</a> | [New Issue...](https://github.com/MicrosoftEdge/MSEdgeExplainers/issues/new?assignees=joone&labels=DelayedMessages&title=%5BDelayedMessages%5D+%3CTITLE+HERE%3E) | Web Perf |
-| [Back to Opener: Seamless Back Navigation in New Tabs](BackToOpener/explainer.md) | <a href="https://github.com/MicrosoftEdge/MSEdgeExplainers/labels/BackToOpener">![GitHub issues by-label](https://img.shields.io/github/issues/MicrosoftEdge/MSEdgeExplainers/BackToOpener?label=issues)</a> | [New Issue...](https://github.com/MicrosoftEdge/MSEdgeExplainers/issues/new?assignees=victorhuangwq&labels=BackToOpener&title=%5BBackToOpener%5D+%3CTITLE+HERE%3E) | WHATWG |
 | [Drag Multiple Virtual Files Out of Browser](https://github.com/MicrosoftEdge/MSEdgeExplainers/blob/main/DownloadURL/explainer.md) | <a href="https://github.com/MicrosoftEdge/MSEdgeExplainers/labels/DownloadURL">![GitHub issues by-label](https://img.shields.io/github/issues/MicrosoftEdge/MSEdgeExplainers/DownloadURL?label=issues)</a> | [New Issue...](https://github.com/MicrosoftEdge/MSEdgeExplainers/issues/new?assignees=joone&labels=DownloadURL&title=%5BDownloadURL%5D+%3CTITLE+HERE%3E) | N/A |
 
 # Alumni 🎓
@@ -271,3 +270,4 @@ We'd love to hear your feedback!
 | [Confirmation of Action](Accessibility/ConfirmationOfAction/explainer.md) | This effort is being pursued in a similar proposal, [AriaNotify](Accessibility/AriaNotify/explainer.md)| 2023-11-13 |
 | [PerformanceNavigationTiming Protocol Launch](PerformanceNavigationTimingProtocolLaunchExtensions/explainer.md) | | 2024-04-22 |
 | [Extending Long Tasks API to Web Workers](LongTasks/explainer.md) | Rather than extending the Long Tasks API to monitor long tasks in web workers, we propose introducing [the Delayed Messages API](DelayedMessages/explainer.md) | 2025-06-09 |
+| [Back to Opener: Seamless Back Navigation in New Tabs](BackToOpener/explainer.md) | We are pursuing this feature as a [Chromium feature](https://issues.chromium.org/issues/448173940) instead of a web platform one. | 2025-08-28 |