msglist: On tap recipient header, open msglist anchored at message

[chrisbobbe]

Fixes: #1621
Related: #252

[rajveermalviya]

Thanks @chrisbobbe! LGTM.

[gnprice]

Looking at this, I'm realizing I don't want this behavior when coming from the combined feed or a channel feed (two things I regularly do). In my common workflows, I'm catching up by scrolling those near the end; I see there's some conversation that looks relevant for me; I want to see the conversation from the beginning, or the beginning of what I haven't previously read. So first-unread is exactly what I want.

We had a chat thread where this behavior came up in the context of search, right? I'm not finding it at the moment — it looks like #1621 didn't get mentioned there. Let's discuss in that thread what the logic should be for this.

[chrisbobbe]

I don't think there's a chat thread, there's just what I wrote on the issue:

This will be helpful for:

• msglist: Offer search narrows #252

and should be easy to do.

So I've just started one: #mobile-team > msglist: anchor when tapping recipient header @ 💬

[gnprice]

Sounds good. I ran across this comment today: #252 (comment) and I think it might have been what I was thinking of.

[chrisbobbe]

Closing in favor of #1657 (but I've kept the add-a-missing-test commit).