fix(rules): compute CMD from Strength and Dexterity directly

PF1e (SRD Combat Maneuvers): CMD = 10 + BAB + Strength modifier +
Dexterity modifier + special size modifier. The Tiny-or-smaller
Dex-for-Str substitution is CMB-only, but _maneuver_cmd reused
_maneuver_cmb for the base, so Tiny/Diminutive/Fine creatures got
10 + BAB + 2xDex + size and dropped Strength (live bug on the Tiny PC
ierlieth). The CMD base is now computed with str_mod directly; CMB
keeps its substitution.

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

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

tests/test_maneuvers.py

@@ -461,6 +461,18 @@ def test_small_or_larger_cmb_uses_strength() -> None:
     assert engine._maneuver_cmb(medium) == 2 - 1 + 0  # bab + str + size
 
 
+def test_tiny_or_smaller_cmd_uses_strength_and_dexterity() -> None:
+    # SRD Combat Maneuvers: "CMD = 10 + Base attack bonus + Strength modifier
+    # + Dexterity modifier + special size modifier" — the Tiny-or-smaller
+    # Dex-for-Str substitution is CMB-only. Tiny: str -1, dex +4, bab 2,
+    # size -2 -> 10 + 2 - 1 + 4 - 2 = 13 (not 10 + 2 + 4 - 2 + 4 = 18).
+    engine = make_engine([], [])
+    for size in ("Tiny", "Diminutive", "Fine"):
+        tiny = make_state(_resized(make_combatant("t"), size, 8, 18), "p", (0, 0))
+        expected = 10 + 2 - 1 + 4 + _SIZE_MODIFIERS[size.lower()]
+        assert engine._maneuver_cmd(tiny) == expected
+
+
 def _buffed(spec: Combatant, mods: tuple[StatModifier, ...]) -> CombatantState:
     state = make_state(spec, "p", (0, 0))
     state.active_buffs.append(