Add game event support to the admin client

Everything on the admin GameScript channel so far has been request/reply.
This adds the other direction: subscribe_events() opens a push stream so a
bot can react to the game instead of polling it, consumed either by awaiting
wait_for_event() or via an on_event callback. Both see every event; an event
goes to at most one waiter, and unclaimed ones sit in a bounded buffer.

Sixteen kinds, from two sources. The engine raises no GameScript event for a
vehicle reaching a stop or cargo arriving, so vehicle_arrive, vehicle_depart
and cargo_waiting are synthesised by the bridge sampling state every
`interval` ticks and diffing against the previous sample -- which means a
stop shorter than the interval is never reported, and the first sample only
establishes a baseline. The rest (crashes, industries, towns, companies,
subsidies) are engine events forwarded verbatim. vehicle_lost,
vehicle_waiting_in_depot and vehicle_unprofitable are deliberately absent:
the engine raises those only for AI companies, so a GameScript can never
observe them.

The server-side half lives in the AdminBridge GameScript, which is not in
this repo -- docker/config is gitignored -- so it has to be updated
separately for any of this to work.

Also repoints the scheduled-dispatch E2E test at a dedicated vehicle
(DISPATCH_VEHICLE_ID). It had been silently skipping because vehicle 7
carries a hand-built annual dispatch schedule, which left eight dispatch
methods unverified end to end while check_public_calls.py reported them
green off static analysis of the call sites.

Co-Authored-By: Claude <[email protected]>

lib/openttd/protocol.py

@@ -1,5 +1,5 @@
 import struct
-from enum import IntEnum
+from enum import IntEnum, StrEnum
 
 import monocypher
 from openttd_protocol.wire.exceptions import SocketClosed
@@ -220,6 +220,40 @@ class NetworkAuthenticationMethod(IntEnum):
     X25519_PAKE = 1
     X25519_AuthorizedKey = 2
 
+class GameEventType(StrEnum):
+    """Event kinds the AdminBridge GameScript can push over the Admin Network.
+
+    These are the values of the "event" field of each event dict, and what
+    OpenTTDAdminClient.subscribe_events() and wait_for_event() take. They are plain strings,
+    so a bare "vehicle_arrive" works everywhere a member does.
+
+    The first three are synthesised by the GameScript sampling game state on an interval,
+    because the engine raises no event for them; the rest are engine events forwarded as they
+    happen. VehicleLost, VehicleWaitingInDepot and VehicleUnprofitable have deliberately no
+    entry here: the engine only ever raises those for AI companies, never for a GameScript.
+    """
+
+    # Polled: derived by diffing successive samples of the game state.
+    VehicleArrive = "vehicle_arrive"
+    VehicleDepart = "vehicle_depart"
+    CargoWaiting = "cargo_waiting"
+    # Forwarded straight from the engine's own GameScript events.
+    VehicleCrashed = "vehicle_crashed"
+    StationFirstVehicle = "station_first_vehicle"
+    IndustryOpen = "industry_open"
+    IndustryClose = "industry_close"
+    TownFounded = "town_founded"
+    CompanyNew = "company_new"
+    CompanyInTrouble = "company_in_trouble"
+    CompanyBankrupt = "company_bankrupt"
+    SubsidyOffer = "subsidy_offer"
+    SubsidyOfferExpired = "subsidy_offer_expired"
+    SubsidyAwarded = "subsidy_awarded"
+    SubsidyExpired = "subsidy_expired"
+    # Emitted by the bridge itself, never subscribed to: one poll produced more events than
+    # fit in the per-poll cap and `count` of them were discarded.
+    EventsDropped = "events_dropped"
+
 class OpenTTDProtocol(TCPProtocol):
     """Low-level OpenTTD TCP protocol handler with encryption support."""
     PacketType = PacketGameType