fix(pool_client): broaden __init__ impl area param to Any

Reordering the overloads adjacent to their impls (prior commit) surfaced a
latent mismatch: the impl signature area: _AreaT did not accept overload
signatures binding area to Literal[Area.CN]/_GlobalArea. Per mypy convention
the overload *implementation* signature uses Any; callers still see the
precise overloads.

Author: plutoless

src/agora_agent/pool_client.py

@@ -323,7 +323,7 @@ def __init__(
     def __init__(
         self,
         *,
-        area: _AreaT,
+        area: typing.Any,
         app_id: str,
         app_certificate: str,
         customer_id: typing.Optional[str] = None,
@@ -659,7 +659,7 @@ def __init__(
     def __init__(
         self,
         *,
-        area: _AreaT,
+        area: typing.Any,
         app_id: str,
         app_certificate: str,
         customer_id: typing.Optional[str] = None,