feat: add alternating team turns

src/Domain/CombatEngine.php

@@ -76,6 +76,39 @@ final class CombatEngine
         return $next->withWinner($attacker->teamId);
     }
 
+    public function endTurn(MatchState $match): MatchState
+    {
+        $this->assertMatchActive($match);
+
+        $teamIds = [];
+
+        foreach ($match->units as $unit) {
+            $teamIds[$unit->teamId] = true;
+        }
+
+        $teamIds = array_keys($teamIds);
+        sort($teamIds);
+
+        if ($teamIds !== ['alpha', 'bravo']) {
+            throw new CombatException('Matches require alpha and bravo teams.');
+        }
+
+        $endingTeamId = $match->activeTeamId;
+        $nextTeamId = $endingTeamId === 'alpha' ? 'bravo' : 'alpha';
+        $units = [];
+
+        foreach ($match->units as $unit) {
+            $units[] = $unit->teamId === $nextTeamId ? $unit->startTurn() : $unit;
+        }
+
+        return $match->copy(
+            units: $units,
+            activeTeamId: $nextTeamId,
+            round: $match->round + ($nextTeamId === 'alpha' ? 1 : 0),
+            actionLog: [...$match->actionLog, "{$endingTeamId} ended turn"],
+        );
+    }
+
     private function unitOrFail(MatchState $match, string $unitId): UnitState
     {
         try {