fix(rules): non-stacking types keep best bonus and worst penalty separately (CRB Common Terms - Stacking)

tests/test_effects.py

@@ -111,20 +111,42 @@ class TestNonStackingTypes:
 class TestPenalties:
     """Given: penalties (negative values) with non-stacking types
     When: resolve_modifiers is called
-    Then: least severe penalty is kept (max value)."""
+    Then: the worst penalty per type is kept, and a same-type bonus and
+    penalty apply together (CRB "Common Terms — Stacking")."""
 
-    def test_same_type_penalties_keep_least_severe(self) -> None:
+    def test_same_type_penalties_keep_most_severe(self) -> None:
         mods = [
             StatModifier("attack", -2, "morale"),
             StatModifier("attack", -1, "morale"),
         ]
-        assert resolve_modifiers(mods) == -1
+        assert resolve_modifiers(mods) == -2
 
-    def test_same_type_bonus_and_penalty_keep_most_beneficial(self) -> None:
+    def test_morale_minus2_and_minus4_keep_worst(self) -> None:
+        mods = [
+            StatModifier("attack", -2, "morale"),
+            StatModifier("attack", -4, "morale"),
+        ]
+        assert resolve_modifiers(mods) == -4
+
+    def test_same_type_bonus_and_penalty_both_apply(self) -> None:
         mods = [
             StatModifier("attack", 2, "morale"),
             StatModifier("attack", -1, "morale"),
         ]
+        assert resolve_modifiers(mods) == 1
+
+    def test_morale_plus2_and_minus2_cancel(self) -> None:
+        mods = [
+            StatModifier("attack", 2, "morale"),
+            StatModifier("attack", -2, "morale"),
+        ]
+        assert resolve_modifiers(mods) == 0
+
+    def test_morale_plus2_and_plus1_keep_highest(self) -> None:
+        mods = [
+            StatModifier("attack", 2, "morale"),
+            StatModifier("attack", 1, "morale"),
+        ]
         assert resolve_modifiers(mods) == 2
 
     def test_untyped_penalties_stack(self) -> None:
@@ -167,7 +189,8 @@ class TestMixedStacking:
             StatModifier("attack", -1),
             StatModifier("attack", 1, "dodge"),
         ]
-        assert resolve_modifiers(mods) == 2  # 2 (max morale) + -1 (untyped) + 1 (dodge)
+        # 2 (max morale bonus) + -1 (morale penalty) + -1 (untyped) + 1 (dodge)
+        assert resolve_modifiers(mods) == 1
 
 
 # ── Edge cases ────────────────────────────────────────────────────────────────