preBuilt

Hand the session a node the caller already constructed.

The bootstrap performs all of its usual wiring (mux channels, presence, admission, app-channel envelope) against node instead of constructing its own — the seam that lets a consumer run the full game stack against a test double (e.g. a FakeRaftNode pinned to Leader) under pure virtual time. The caller retains lifecycle ownership of node; GameSession.close still calls RaftNode.close on it as usual.

Seating is AuthoritySeating.SessionPeers: the bootstrap's own membership machinery (roster requires, admission loops) applies unchanged, now driving the provided node.