fix(rules): aid another bonuses expire at the beginning of the aider's next turn, not the beneficiary's (SRD Aid Another)

tests/test_aid_and_run.py

@@ -293,6 +293,32 @@ def test_failed_aid_grants_nothing() -> None:
     assert hero.hp == 97
 
 
+# ── (c2) the aid bonus expires at the AIDER's next turn, not the beneficiary's ─
+
+def test_aid_bonus_survives_beneficiary_turn_and_expires_at_aider_turn() -> None:
+    # SRD "Aid Another": the +2 lasts "as long as that attack comes before the
+    # beginning of your next turn" — your = the AIDER's. The ally aids the
+    # hero (ac) in round 1; the hero's own round-2 turn start must NOT clear
+    # the bonus, the ally's round-2 turn start must.
+    seen: dict[str, int] = {}
+
+    def policy(engine: CombatEngine, state: CombatantState) -> tuple[Action, ...]:
+        cid = state.combatant.id
+        if cid == "hero" and engine._current_round == 2:
+            seen["hero_turn"] = state.aid_ac_bonus
+        if cid == "foe" and engine._current_round == 2:
+            seen["foe_turn"] = engine._states[0].aid_ac_bonus
+        if cid == "ally" and engine._current_round == 1:
+            return (Action(kind="aid_another", target_id="hero", aid_mode="ac"),)
+        return _WAIT
+
+    # Rolls: 3 initiatives (10,10,10); aid d20=10+5=15 >= 10 success.
+    eng = _trio(policy, [10, 10, 10, 10], round_cap=2)
+    eng.run()
+    assert seen["hero_turn"] == 2  # survived the beneficiary's turn start
+    assert seen["foe_turn"] == 0  # expired at the aider's turn start
+
+
 # ── (d) run moves up to 4x speed (destination and target), sets running ──────