tidyprompt 0.4.0

• New prompt wrap answer_as_dataframe() for extracting tabular results via
  structured output, with support for row schemas, array-of-row schemas,
  and optional row-count validation.

• New prompt wrap answer_as_numeric() for extracting numeric responses,
  including optional minimum and maximum value validation.

• send_prompt() can now directly use an 'ellmer' chat object as
  the llm_provider to evaluate the prompt with (will build
  an llm_provider_ellmer() under the hood)

• llm_provider_ellmer() was improved to better synchronize with
  the native 'ellmer' state, for instance for streaming, multimodal/image
  content, and persistent chats, with clearer warnings when settings need to
  be configured on the underlying ellmer chat object.

• answer_as_json() and answer_using_tools() have broader ellmer
  compatibility, including ellmer::type_from_schema(), ellmer built-in tools,
  and better handling of optional or ignored tool arguments.

• Chat history handling is more robust for tool and ellmer-native workflows:
  tool rows are supported, non-replayable native rows (tool call and thinking rows)
  are kept for inspection but not re-sent to the LLM provider, and related
  metadata is normalized more reliably.

• Update e-mail address of maintainer in DESCRIPTION file
  (change to a personal e-mail address due to leaving the organization).