feat: add reasoning token support to Mistral integration

[ArkaD171717]

Mistral returns reasoning as array content blocks:
content: [{"type": "thinking", ...}, {"type": "text", ...}]

The OpenAI SDK expects content: str | None and throws a Pydantic
ValidationError when it sees this
Non-streaming calls now use with_raw_response to get the raw JSON and parse
it manually, sidestepping SDK validation entirely
Streaming still goes through the normal SDK path since it processes
token-by-token (a warning is logged that reasoning content won't be captured
during streaming)

reasoning_effort and prompt_mode are routed through extra_body since
they're Mistral-specific params that the OpenAI SDK would reject as unknown
kwargs

Multi-turn reasoning is handled the same way as the OpenRouter PR: re-inject
array content into the formatted message dicts in _prepare_api_call

Also cleaned up duplicate entries in SUPPORTED_MODELS

25 new tests covering sync, async, multi-turn, edge cases
(unexpected content types, empty messages, JSON string parsing, async empty
messages, async streaming reasoning warning)
All 16 existing tests still pass

Closes #2180

[CLAassistant]

All committers have signed the CLA.

[github-actions]

Heads-up for maintainers

This PR is from a fork and touches integrations whose integration tests require API keys.
Those tests are skipped in CI because fork PRs don't have access to repo secrets for security reasons.

Affected integrations:

• mistral

Please run the integration tests locally (hatch run test:integration inside each folder) before approving.

[github-actions]

Coverage report (mistral)

Click to see where and how coverage changed

File	Statements	Missing	Coverage	Coverage (new stmts)	Lines missing
integrations/mistral/src/haystack_integrations/components/generators/mistral/chat
chat_generator.py					306, 386-387, 454-455
Project Total

This report was generated by python-coverage-comment-action

[ArkaD171717]

Brought up to date

[bogdankostic]

Hi @ArkaD171717, thanks for creating this PR!

Unfortunately, 9 of the integration tests are failing. Almost all of them seem to share the same root cause related to the API response: AttributeError: 'LegacyAPIResponse' object has no attribute 'json'.

FAILED tests/test_mistral_chat_generator.py::TestMistralChatGenerator::test_live_run - AttributeError: 'LegacyAPIResponse' object has no attribute 'json'
FAILED tests/test_mistral_chat_generator.py::TestMistralChatGenerator::test_live_run_response_format - AttributeError: 'LegacyAPIResponse' object has no attribute 'json'
FAILED tests/test_mistral_chat_generator.py::TestMistralChatGenerator::test_live_run_with_response_format_json_schema - AttributeError: 'LegacyAPIResponse' object has no attribute 'json'
FAILED tests/test_mistral_chat_generator.py::TestMistralChatGenerator::test_live_run_with_tools - AttributeError: 'LegacyAPIResponse' object has no attribute 'json'
FAILED tests/test_mistral_chat_generator.py::TestMistralChatGenerator::test_live_run_with_tools_and_response - AttributeError: 'LegacyAPIResponse' object has no attribute 'json'
FAILED tests/test_mistral_chat_generator.py::TestMistralChatGenerator::test_pipeline_with_mistral_chat_generator - haystack.core.errors.PipelineRuntimeError: The following component failed to run:
FAILED tests/test_mistral_chat_generator.py::TestMistralChatGenerator::test_live_run_with_mixed_tools - AttributeError: 'LegacyAPIResponse' object has no attribute 'json'
FAILED tests/test_mistral_chat_generator_async.py::TestMistralChatGeneratorAsync::test_live_run_async - AttributeError: 'LegacyAPIResponse' object has no attribute 'json'
FAILED tests/test_mistral_chat_generator_async.py::TestMistralChatGeneratorAsync::test_live_run_with_tools_and_response_async - AttributeError: 'LegacyAPIResponse' object has no attribute 'json'

Let us know if you need any help reproducing these test failures locally! Just a heads-up: running these tests requires a Mistral API key.

[ArkaD171717]

@bogdankostic Thanks for running the integration tests! The issue was that with_raw_response returns a LegacyAPIResponse in the SDK version pinned here which doesnt have .json(). Switched to .text which is available on both LegacyAPIResponse and APIResponse. I updated the test mocks to match and shld be fixed in the latest push.

LMK if any tests are still failing

[bogdankostic]

Thanks @ArkaD171717! I added two integration tests and the PR should be good to go now :)