fix(rules): apply cover by attacker's best corner for multi-square attackers

src/pf1e_simulator/los.py

@@ -254,9 +254,12 @@ def cover_bonus_cells(
     """Effective cover bonus (0/2/4/8) for an attack between two sets of cells.
 
     0 when there is no cover (see has_cover_cells for the corner rule);
-    otherwise the highest cover level among the cells blocking the
-    attacker-corner to target-corner lines. Interposed creatures grant soft
-    cover (+4) on ranged attacks only, exactly as in has_cover_cells.
+    otherwise the cover level of the attacker's BEST occupied cell: each
+    attacker cell is scored by the per-cell corner rule against all of the
+    target's cells, and the attacker picks the lowest-scoring (clearest)
+    cell. Interposed creatures grant soft cover (+4) on ranged attacks only,
+    exactly as in has_cover_cells. For a 1x1 attacker this is exactly the
+    single-cell value.
     """
     if not attacker_cells or not target_cells:
         return 0
@@ -271,10 +274,18 @@ def cover_bonus_cells(
         occupied if ranged else frozenset(),
         bonus_of=terrain_cover_bonus,
     )
-    return max(
-        lines.bonus(corner_a, corner_t)
+    # PF1e CRB "Cover", rule of corners: the attacker chooses the corner (and,
+    # for a multi-square creature, the occupied square) that gives it the best
+    # shot, so it suffers only the MINIMUM cover over its own cells. The
+    # target side is unchanged: RAW checks ANY line to ANY target corner, so
+    # each attacker cell is scored by the MAXIMUM over its corner lines.
+    per_cell_best = (
+        max(
+            lines.bonus(corner_a, corner_t)
+            for corner_a in _corners(cell_a)
+            for cell_t in target_cells
+            for corner_t in _corners(cell_t)
+        )
         for cell_a in attacker_cells
-        for corner_a in _corners(cell_a)
-        for cell_t in target_cells
-        for corner_t in _corners(cell_t)
     )
+    return min(per_cell_best)