Show who has joined the team directory #605

Nothing shows who has joined a team directory, or tells the person serving it that someone joined.

What was seen

B serves the directory, and A joined it. B looked for a member list in the Directory row, Refresh, People, "Add a teammate" and the Dashboard. The only member view was the one-off "Your team's directory is running" dialog right after creation ("samechocolixir · Serving", "iamnbutler · Joins now"), and it can't be reopened. B: "Nothing on my side changed when A joined. There's no notice, no 'joined' state, and no member count." People looks the same before and after a directory exists, so neither tester could tell whether it came from the directory or the tailnet.

Steps

1. Create a directory on This Mac; a teammate joins it.
2. On the serving Mac, look for who has joined.

Expected: Settings → Team lists the directory's hosts and when each last synced.

Map: ^901. Part of #550.

Found in the 2026-10-22 two-Mac pair study.