Halt sim on A2A contact.

https://github.com/dcs-liberation/dcs_liberation/issues/1681

game/ato/flightstate/loiter.py

@@ -0,0 +1,38 @@
+from __future__ import annotations
+
+from datetime import timedelta
+from typing import TYPE_CHECKING
+
+from dcs import Point
+
+from game.ato.flightstate import FlightState, InFlight
+from game.utils import Distance, Speed
+from gen.flights.flightplan import LoiterFlightPlan
+
+if TYPE_CHECKING:
+    from game.ato.flight import Flight
+    from game.settings import Settings
+
+
+class Loiter(InFlight):
+    def __init__(self, flight: Flight, settings: Settings, waypoint_index: int) -> None:
+        assert isinstance(flight.flight_plan, LoiterFlightPlan)
+        self.hold_duration = flight.flight_plan.hold_duration
+        super().__init__(flight, settings, waypoint_index)
+
+    def estimate_position(self) -> Point:
+        return self.current_waypoint.position
+
+    def estimate_altitude(self) -> tuple[Distance, str]:
+        return self.current_waypoint.alt, self.current_waypoint.alt_type
+
+    def estimate_speed(self) -> Speed:
+        return self.flight.unit_type.preferred_patrol_speed(self.estimate_altitude()[0])
+
+    def next_waypoint_state(self) -> FlightState:
+        # Do not automatically advance to the next waypoint. Just proceed from the
+        # current one with the normal flying state.
+        return InFlight(self.flight, self.settings, self.waypoint_index)
+
+    def travel_time_between_waypoints(self) -> timedelta:
+        return self.hold_duration