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]>

main_admin.py

@@ -7,7 +7,7 @@ import sys
 sys.path.append(os.path.join(os.path.dirname(__file__), 'lib'))
 
 from openttd import OpenTTDAdminClient
-from openttd.protocol import AdminUpdateFrequency, AdminUpdateType
+from openttd.protocol import AdminUpdateFrequency, AdminUpdateType, GameEventType
 
 # Configuration
 SERVER_HOST = "127.0.0.1"
@@ -85,7 +85,26 @@ async def run_admin():
             except Exception as e:  # noqa: BLE001 - demo script: one failed station query should not abort the walk
                 print(f"!!! station query failed: {e}")
 
-        await asyncio.sleep(5)
+        # Watch the game live: vehicles reaching/leaving stops and cargo piling up at stations.
+        print("--- Subscribing to game events ---")
+        try:
+            accepted = await admin.subscribe_events(
+                events=[GameEventType.VehicleArrive, GameEventType.VehicleDepart,
+                        GameEventType.CargoWaiting],
+                interval=5, timeout=10.0)
+            print(f"    subscribed to {accepted['events']} every {accepted['interval']} ticks")
+
+            for _ in range(5):
+                try:
+                    event = await admin.wait_for_event(timeout=15.0)
+                except asyncio.TimeoutError:
+                    print("    (nothing happened -- is the server paused or idle?)")
+                    break
+                print(f">>> [EVENT] {event}")
+            await admin.unsubscribe_events()
+        except Exception as e:  # noqa: BLE001 - demo script: report and carry on to a clean quit
+            print(f"!!! event subscription failed: {e}")
+
         print("--- Quitting ---")
         await admin.quit()