fix: remove seed from DEFAULT_MODEL_CONFIG

Google's OpenAI-compatible API rejects requests that include the
`seed` parameter with 400 INVALID_ARGUMENT. The `seed` field is
not part of the OpenAI-compatible spec that Google implements.

Removing it from the defaults fixes compatibility with Google's
Generative Language API while not affecting providers that do
support it (users can still set it via model_config in YAML).

Author: felipefl142

src/balatrollm/config.py

@@ -16,7 +16,6 @@
 ################################################################################
 
 DEFAULT_MODEL_CONFIG: dict[str, bool | int | str | dict] = {
-    "seed": 1,
     "parallel_tool_calls": False,
     "tool_choice": "auto",
     "extra_headers": {