The per-connection list cache is kept only to repaint $profiles on re-home.
The $fleetRoster listener is dropped: a roster landing while the active
source's own /api/profiles read was in flight invalidated that read, so
$profiles stayed empty/stale after every switch or focus refresh that the
roster IPC won. Both are reads of the same backend; neither is "older".
A null descriptor is a reconnect blip (setConnection's contract) and keeps
the current owner instead of blanking the rail; the first published
descriptor adopts whatever list is already loaded. Legacy sources are keyed
by endpoint rather than a JSON tuple. Tests cover the roster race and the
null blip; the two use-session-actions tests now publish the descriptor
before seeding $profiles, matching the runtime order.
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