openDm reloaded every membership, profile, and latest message before
returning, so the New message sheet's spinner could run for many seconds
on a large account or slow connection. Interactive opens (New message,
Search, profile) now open the DM from its own metadata and roster and
reconcile the channel list in the background, as Solo chat creation
already does. Hidden-DM resurfacing keeps waiting for the list, which
is what clears its hidden state.
Signed-off-by: Tom Brow <tomb@block.xyz>
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