AgentHost: Remote session stops updating after connection change

[roblourens]

• Have a remote AH session running
• I end up reconnecting to the remote due to a network change (I think)
• The remote session is paused in the view, shows in progress, but actually is complete

When I open the session, we subscribe, we get the full complete content from the AH, but don't render it. We reuse an existing stale ChatModel, kept open due to ChatModel#requestInProgressKeepAlive, and do not go through provideChatSessionContent