- Fix type of `AssistantChatMessage.role` to match `ChatMessage.role` (str -> `ChatMessage.Role`)
- Simplify `ModelProviderUsage`
   - Remove attribute `total_tokens` as it is always equal to `prompt_tokens + completion_tokens`
   - Modify signature of `update_usage(..)`; no longer requires a full `ModelResponse` object as input
- Improve `ModelProviderBudget`
   - Change type of attribute `usage` to `defaultdict[str, ModelProviderUsage]` -> allow per-model usage tracking
   - Modify signature of `update_usage_and_cost(..)`; no longer requires a full `ModelResponse` object as input

Also:
- Remove unused `OpenAIChatParser` typedef in openai.py
- Remove redundant `budget` attribute definition on `OpenAISettings`
- Remove unnecessary `usage` in `OpenAIProvider` > `default_settings` > `budget`

yee haw!

Also:
- Add `ToolResultMessage` to `model_providers.schema`

…ider`

…ompletion` interface

…emove `ApiManager`

…ntiation

Also:
- straighten out related model definitions
    - remove now-redundant `service=` arguments for `ChatModelInfo`/`EmbeddingModelInfo` usages
- use `defaultdict(ModelProviderBudget)` in agent_protocol_server.py to simplify budget tracking setup

…Provider` base class

…t_completion_call`

in `processing/text.py:_process_text`

…ovider`

- Add `MultiProvider`
- Replace all references to / uses of `OpenAIProvider` with `MultiProvider`
- Change type of `Config.smart_llm` and `Config.fast_llm` from `str` to `ModelName`

… to not-our-fault errors

So e.g. don't retry on 400 Bad Request errors or anything else in the 4xx range

10 was too much, caused multi-minute timeouts between retries

…echanism

If assistant  message contains `tool_use` blocks, include required `tool_result` blocks in feedback message

…mpletion`

- Add `validate_call` method to `CompletionModelFunction` in `model_providers.schema`
- Add `validate_tool_calls` utility function in `model_providers.utils`
- Add tool call validation step to `create_chat_completion` in `OpenAIProvider` and `AnthropicProvider`

Also:
- Remove (now redundant) command argument validation logic in agent.py and models/command.py

- Add `prefill_response` attribute to `ChatPrompt` model
- Add `prefill_response` parameter to `ChatModelProvider.create_chat_completion` and its implementations
- Amend `OneShotAgentPromptStrategy` to use new pre-filling feature

… prompt"

This reverts commit c10fafa.

…ovider._get_chat_completion_args`

This reverts commit 70c97ca.