fix(rules): apply AC penalties to CMD

PF1e (SRD Combat Maneuvers): "Any penalties to a creature's AC also
apply to its CMD." _maneuver_cmd now folds negative AC modifiers into the
sum regardless of bonus type (grappled -2, other untyped penalties), and —
a maneuver being a melee attack roll — the prone -4 melee AC penalty.
Positive modifiers keep the eight SRD-listed types. The test that pinned
the old ignore-penalties convention is updated; README documents the rule.

Ultraworked with [Sisyphus](https://github.com/code-yeongyu/oh-my-openagent)

Co-authored-by: Sisyphus <clio-agent@sisyphuslabs.ai>

tests/test_maneuvers.py

@@ -504,9 +504,10 @@ def test_cmd_adds_eligible_ac_bonus_types() -> None:
     assert engine._maneuver_cmd(buffed) == 12 + 4 + 2
 
 
-def test_cmd_ignores_non_ac_bonus_types() -> None:
-    # Enhancement/natural armor bonuses and untyped penalties are NOT added
-    # to CMD (only the eight SRD-listed AC bonus types are).
+def test_cmd_ignores_non_ac_bonus_types_keeps_penalties() -> None:
+    # Enhancement bonuses are NOT among the eight SRD-listed types — ignored.
+    # But "Any penalties to a creature's AC also apply to its CMD" (SRD
+    # Combat Maneuvers): the untyped -4 penalty rides the CMD.
     engine = make_engine([], [])
     state = _buffed(
         make_combatant("b"),
@@ -515,7 +516,28 @@ def test_cmd_ignores_non_ac_bonus_types() -> None:
             StatModifier(target="ac", value=-4),
         ),
     )
-    assert engine._maneuver_cmd(state) == 12
+    assert engine._maneuver_cmd(state) == 12 - 4
+
+
+def test_cmd_includes_prone_and_grappled_penalties() -> None:
+    # A maneuver is a melee attack roll, so the prone -4 melee AC penalty and
+    # the grappled -2 AC penalty both apply to CMD (SRD: "Any penalties to a
+    # creature's AC also apply to its CMD").
+    engine = make_engine([], [])
+    prone = make_state(make_combatant("p"), "p", (0, 0))
+    prone.active_conditions.append(
+        ActiveCondition(
+            condition=CONDITIONS_BY_NAME["prone"], rounds_left=1, source="test"
+        )
+    )
+    assert engine._maneuver_cmd(prone) == 12 - 4
+    grappled = make_state(make_combatant("g"), "p", (0, 1))
+    grappled.active_conditions.append(
+        ActiveCondition(
+            condition=CONDITIONS_BY_NAME["grappled"], rounds_left=1, source="test"
+        )
+    )
+    assert engine._maneuver_cmd(grappled) == 12 - 2
 
 
 def test_cmd_flat_footed_drops_dex_bonus_keeps_penalty() -> None: