test(proxy): give the spend counter test fakes the reset fence hook

CountingRedis skipped RedisCache.__init__ and _ExpiringRedisCache never had reset_fence_key, so the repair's broad except swallowed the AttributeError and the counter stayed stale in five tests

tests/unit/proxy/spend_tracking/test_spend_counter_batch.py

@@ -41,6 +41,7 @@ class CountingRedis(RedisCache):
         self.store: dict[str, object] = dict(store or {})
         self.fail = fail
         self.commands: list[str] = []
+        self.namespace = None
 
     async def async_get_cache(self, key: str, **kwargs: object) -> object:
         if self.fail:

tests/unit/proxy/test_budget_reservation.py

@@ -2366,6 +2366,9 @@ class _ExpiringRedisCache:
         self.expires_at[key] = self._expiry(kwargs.get("ttl"))
         return self.store[key]
 
+    def reset_fence_key(self, key: str) -> str:
+        return f"{{{key}}}:reset_fence"
+
     async def async_set_max(self, key: str, value: float, **kwargs: object) -> float:
         self._evict_expired(key)
         self.store[key] = max(self.store.get(key, float("-inf")), float(value))