Group together same-thread notifications to reduce newsfeed clutter.

In my opinion, this is too redundant having multiple, consecutive, separate notifications for the same thread, and this is easily spammable.

Start by locating the JavaScript code responsible for rendering newsfeed notifications, using the attached screenshot and the issue description as the expected behavior. Trace how notifications identify their threads and determine where consecutive same-thread items are displayed. Done means repeated notifications for one thread are grouped rather than shown as separate consecutive entries.

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