feat(rails): answer RequestRailActivatorState

The client's rail activator sends RequestRailActivatorState (1479, no
payload) when it is added to the world (LWORailActivatorComponent::
SendMessage 0x00c00da0) and live answered with
NotifyRailActivatorStateChange (1478, bActive) to that client; the client
stores rail_activator_active and updates the rail's pick type (usable or
not). Live: 152 requests, 413 answers, every one bActive = true. DLU
dropped the request and never answered.

RailActivatorComponent keeps the level key rail_activator_active
(default true; every rail in the live levels sets it to 1) and the
request is answered with it.

Check in game: in Ninjago Monastery and Nimbus Station, rails (spinjitzu
posts, the Nexus Tower rails) show as usable and work as before when
first loading the world and after zone changes.

Co-Authored-By: Claude Opus 5.5 <noreply@anthropic.com>

dGame/dGameMessages/GameMessageHandler.cpp

@@ -215,6 +215,7 @@ namespace {
 		{ CLIENT_RAIL_MOVEMENT_READY, []() { return std::make_unique<ClientRailMovementReady>(); } },
 		{ CANCEL_RAIL_MOVEMENT, []() { return std::make_unique<CancelRailMovement>(); } },
 		{ PLAYER_RAIL_ARRIVED_NOTIFICATION, []() { return std::make_unique<PlayerRailArrivedNotification>(); } },
+		{ REQUEST_RAIL_ACTIVATOR_STATE, []() { return std::make_unique<RequestRailActivatorState>(); } },
 		{ DISMOUNT_COMPLETE, []() { return std::make_unique<DismountComplete>(); } },
 		{ ACKNOWLEDGE_POSSESSION, []() { return std::make_unique<AcknowledgePossession>(); } },
 		{ TOGGLE_GHOST_REFERENCE_OVERRIDE, []() { return std::make_unique<ToggleGhostReferenceOverride>(); } },