fix(config): return provider default api base in config resolution

nanobot/config/schema.py

@@ -304,17 +304,15 @@ class Config(BaseSettings):
         return p.api_key if p else None
 
     def get_api_base(self, model: str | None = None) -> str | None:
-        """Get API base URL for the given model. Applies default URLs for gateway/local providers."""
+        """Get API base URL for the given model, falling back to the provider default when present."""
         from nanobot.providers.registry import find_by_name
 
         p, name = self._match_provider(model)
         if p and p.api_base:
             return p.api_base
-        # Only gateways get a default api_base here. Standard providers
-        # resolve their base URL from the registry in the provider constructor.
         if name:
             spec = find_by_name(name)
-            if spec and (spec.is_gateway or spec.is_local) and spec.default_api_base:
+            if spec and spec.default_api_base:
                 return spec.default_api_base
         return None