Let a transport point this server at the ConnectionState it owns for a
mount/connection at wire-up (mountMcp / runStdio / serveStdio). Used
by the notify/push path, which fires OUTSIDE any request and therefore
cannot receive the state as a dispatch argument. This sets the fallback
activeConnection; HTTP requests still resolve their own per-session state.
Let a transport point this server at the ConnectionState it owns for a mount/connection at wire-up (mountMcp / runStdio / serveStdio). Used by the notify/push path, which fires OUTSIDE any request and therefore cannot receive the state as a dispatch argument. This sets the fallback activeConnection; HTTP requests still resolve their own per-session state.