Closing a search page no longer drops the connection

Leaving a search or catalog page at the moment fresh results arrived could break the page's connection to the server, showing the reconnecting overlay for no reason. Tidying up the page's live subscriptions collided with results still coming in.

Views now tear their subscriptions down in a way that tolerates late arrivals, so leaving a page is never disruptive. The same change also stops a subscription that arrives during teardown from being left running for a page that is already gone.