feat(init): Replace create_chat_func with client

[gadenbuie]

Fixes #58

Python

querychat.init() now accepts a client argument, replacing the previous create_chat_callback argument.

The client can be:

• a chatlas.Chat object,
• a function that returns a chatlas.Chat object,
• or a provider-model string, e.g. "openai/gpt-4.1", to be passed to chatlas.ChatAuto().

If client is not provided, querychat will use the QUERYCHAT_CLIENT environment variable, which should be a provider-model string. If the envvar is not set, querychat uses OpenAI with the default model from chatlas.ChatOpenAI().

R

querychat_init() now accepts a client, replacing the previous create_chat_func argument.

The client can be:

• an ellmer::Chat object,
• a function that returns an ellmer::Chat object,
• or a provider-model string, e.g. "openai/gpt-4.1", to be passed to ellmer::chat().

If client is not provided, querychat will use

• the querychat.client R option, which can be any of the above options,
• the QUERYCHAT_CLIENT environment variable, which should be a provider-model string,
• or the default model from ellmer::chat_openai().