fix: Enhances alias resolution with type check

Replaces a dictionary key existence check with an instance
check, ensuring the response is of the expected type
RoomResolveAliasResponse. This improves robustness by
relying on a concrete type instead of assuming dictionary
structure.

src/matrix_roomba/bot.py

@@ -140,8 +140,8 @@ class RoombaBot:
         """
         response = await self.client.room_resolve_alias(room_alias)
 
-        if response and "room_id" in response:
-            return response["room_id"]
+        if isinstance(response, nio.RoomResolveAliasResponse):
+            return response.room_id
 
         return room_alias