fix: raise error when request param failed to convert (#1339)

# Summary:
This led to extremely hard to debug messages.
Before:

llama_stack/distribution/library_client.py:275: in request
    response = await self._call_non_streaming(
llama_stack/distribution/library_client.py:322: in _call_non_streaming
    result = await matched_func(**body)
llama_stack/providers/utils/telemetry/trace_protocol.py:102: in
async_wrapper
    result = await method(self, *args, **kwargs)
llama_stack/providers/inline/agents/meta_reference/agents.py:80: in
create_agent
    value=agent_config.model_dump_json(),
E   AttributeError: 'dict' object has no attribute 'model_dump_json'

After:

E ValueError: Failed to convert parameter {'model':
'meta-llama/Llama-3.1-8B-Instruct', 'instructions': 'You are a helpful
assistant', 'sampling_params': {'strategy': {'type': 'top_p',
'temperature': 0.0001, 'top_p': 0.9}}, 'toolgroups': [{'name':
'builtin::rag'}], 'input_shields': ['meta-llama/Llama-Guard-3-8B'],
'output_shields': ['meta-llama/Llama-Guard-3-8B'],
'enable_session_persistence': False} into <class
'llama_stack.apis.agents.agents.AgentConfig'>: 2 validation errors for
AgentConfig
E   toolgroups.0.str
E Input should be a valid string [type=string_type, input_value={'name':
'builtin::rag'}, input_type=dict]
E For further information visit
https://errors.pydantic.dev/2.10/v/string_type
E   toolgroups.0.AgentToolGroupWithArgs.args
E Field required [type=missing, input_value={'name': 'builtin::rag'},
input_type=dict]
E For further information visit
https://errors.pydantic.dev/2.10/v/missing

# Test Plan:
LLAMA_STACK_CONFIG=fireworks pytest -s -v tests/client-sdk/
--safety-shield meta-llama/Llama-Guard-3-8B

llama_stack/distribution/library_client.py

@@ -104,7 +104,7 @@ def convert_to_pydantic(annotation: Any, value: Any) -> Any:
             logger.warning(
                 f"Warning: direct client failed to convert parameter {value} into {annotation}: {e}",
             )
-        return value
+        raise ValueError(f"Failed to convert parameter {value} into {annotation}: {e}") from e
 
 
 class LlamaStackAsLibraryClient(LlamaStackClient):