control/controlclient: de-pointer Status.PersistView, document more

Updates #cleanup
Updates #1909

Change-Id: I31d91e120e3b299508de2136021eab3b34131a44
Signed-off-by: Brad Fitzpatrick <bradfitz@tailscale.com>
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Internal Server Error - Gitea: Git with a cup of tea
500 Internal Server Error

Gitea Version: 1.28.0+dev-477-g8b6ad49a5f