feat(combat): grant soft cover (+4 AC) to ranged attacks through creatures

src/pf1e_simulator/combat.py

@@ -15,11 +15,12 @@ Phase 0 documented deviations from PF1e (conventions):
 - Line of effect gates all attacks: a target fully behind blocking terrain
   cannot be attacked, and the policy moves to gain sight instead.
 - Cover (corner rule) grants +4 AC on hit and crit-confirm rolls; melee and
-  ranged reuse the same corner rule.
+  ranged reuse the same corner rule. Soft cover: active creatures between
+  attacker and target also grant +4 AC on ranged attacks (CRB soft cover);
+  melee attacks ignore creatures.
 - Ranged: cumulative -2 per full range increment beyond the first, up to 10
   range increments; the penalty applies to attack and crit-confirm rolls.
-  Thrown weapons (5 increments max) are not distinguished; soft cover from
-  creatures is not modeled.
+  Thrown weapons (5 increments max) are not distinguished.
 """
 
 from __future__ import annotations
@@ -221,7 +222,16 @@ class CombatEngine:
         penalty = self.range_penalty(weapon, dist_ft)
         total = roll + weapon.attack_bonus + penalty
         ac = target.combatant.ac.total
-        if has_cover(self._grid, attacker.pos, target.pos, ranged=weapon.kind == "ranged"):
+        occupied = frozenset(
+            s.pos for s in self._states if s.active and s is not attacker and s is not target
+        )
+        if has_cover(
+            self._grid,
+            attacker.pos,
+            target.pos,
+            ranged=weapon.kind == "ranged",
+            occupied=occupied,
+        ):
             ac += _COVER_AC_BONUS
         hit = roll == _NATURAL_TWENTY or (roll != _NATURAL_ONE and total >= ac)
         crit = False