Fix some CAS planning quirks.

CAS would never be planned for turn 0 because there were no enemy ground
units, so a breakthrough attack was planned and CAS was considered
unnecessary. Fix that by rejecting all frontline stance tasks when there
are no *friendly* ground units to command.

Another issue is that CAS missions were being planned even when there
were no enemy front line forces. Skip planning in that case except on
turn 0 since we expect there to be enemy ground units on turn 1.

Fixes https://github.com/dcs-liberation/dcs_liberation/issues/1629

game/commander/tasks/frontlinestancetask.py

@@ -66,6 +66,8 @@ class FrontLineStanceTask(TheaterCommanderTask, ABC):
             return False
         if self.better_stance_already_set(state):
             return False
+        if self.friendly_cp.deployable_front_line_units == 0:
+            return False
         return self.have_sufficient_front_line_advantage
 
     def apply_effects(self, state: TheaterState) -> None:

game/commander/tasks/primitive/cas.py

@@ -13,6 +13,16 @@ class PlanCas(PackagePlanningTask[FrontLine]):
     def preconditions_met(self, state: TheaterState) -> bool:
         if self.target not in state.vulnerable_front_lines:
             return False
+
+        # Do not bother planning CAS when there are no enemy ground units at the front.
+        # An exception is made for turn zero since that's not being truly planned, but
+        # just to determine what missions should be planned on turn 1 (when there *will*
+        # be ground units) and what aircraft should be ordered.
+        enemy_cp = self.target.control_point_friendly_to(
+            player=not state.context.coalition.player
+        )
+        if enemy_cp.deployable_front_line_units == 0 and state.context.turn > 0:
+            return False
         return super().preconditions_met(state)
 
     def apply_effects(self, state: TheaterState) -> None:

game/commander/theaterstate.py

@@ -34,6 +34,7 @@ if TYPE_CHECKING:
 class PersistentContext:
     coalition: Coalition
     theater: ConflictTheater
+    turn: int
     settings: Settings
     tracer: MultiEventTracer
 
@@ -139,7 +140,9 @@ class TheaterState(WorldState["TheaterState"]):
         finder = ObjectiveFinder(game, player)
         ordered_capturable_points = finder.prioritized_unisolated_points()
 
-        context = PersistentContext(coalition, game.theater, game.settings, tracer)
+        context = PersistentContext(
+            coalition, game.theater, game.turn, game.settings, tracer
+        )
 
         # Plan enough rounds of CAP that the target has coverage over the expected
         # mission duration.