Highlight currently circulating viruses

[genehack]

Extracted from priorities meeting notes; issue created to track progress.

Ticket assignment based on lead in notes.

Related PRs

• Include 21L rooted Nextstrain build for GISAID data #1029
• Include profile for open 21L builds #1101
• Restrict 6m builds to tips in the last 6m (post-tree-building) #934
• Restrict contextual samples to 1 year back in 1m/2m/6m builds #1129
• Gray out early clades #1132
• Include default zoom in Auspice defaults auspice#1946

[victorlin]

I've linked to related PRs in the issue description and updated individual PRs to clarify what's been tried, what's been done, and what is still on the table.

@trvrb do you think it's still worth pushing #1101 through?

[trvrb]

My sense is that including the additional context back to Wuhan is still useful, ie

despite the fact this context is now taking up 90% of the horizontal space on the page (it's still only a click away to zoom in to relevant circulating viruses). I think however that we will need to move to a "flu-like" system like #1129 in a year or so. At that time we should add a 2y option and also remove the 21L builds.

This leaves open/21L in a weird place. It should have gotten made alongside gisaid/21L, but now we think we'll be deprecating gisaid/21L in the coming months. I'd probably close #1129 in this case.