Result envelopes and the scene readers that snapshot and remoteActivity both use.

# AFTERCURRENT multiplayer test bench Answers the questions a screenshot cannot: which race a peer is actually in, which cars it holds and who owns them, and whether anything a remote peer sends is reaching this engine at all. Run the same tool on each peer and compare the records side by side. 1. `tools.use("rainlineTest","snapshot")` — this peer's honest state: its id, every Race component in the scene with its clock and roster, and every car with its owner, whether this peer drives it, and whether it is drawn. 2. `tools.use("rainlineTest","remoteActivity",6)` — watch every entity this peer does NOT own for six seconds and report which of them changed. Nothing changing means replication is not arriving, which is a different fault from a car that is present but parked. 3. `tools.use("rainlineTest","press","title_multiplayer")` — press a real menu button by its callback id, so a test walks the path a player walks instead of setting the flags the menu would have set. Button ids: `title_drive`, `title_multiplayer`, `rainline_enter`, `lobby_vote_1`..`lobby_vote_5`, `lobby_leave`, `rainline_restart`.