fix(types): add top_logprobs to LogprobsPart to match API response shape

[xodn348]

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Issue #443

Describe your changes

LogprobsPart (in src/together/types/common.py) was missing a typed field for top_logprobs, even though the Together API returns it alongside tokens and token_logprobs when logprobs=N is requested.

Because BaseModel uses extra="allow", the data was silently stored as an untyped extra attribute. Two problems result:

1. No static type information — IDEs and mypy treat response.choices[0].logprobs.top_logprobs as Any, losing all type safety.
2. PydanticSerializationUnexpectedValue warnings on model_dump() — when serializing, Pydantic sees a list value for a field that has no declared schema and emits a warning.

The fix adds:

top_logprobs: List[Dict[str, float]] | None = None

to LogprobsPart, matching the actual API shape: one dict per token mapping each candidate token string to its log-probability.

Three unit tests are added to tests/unit/test_logprobs_type.py:

• Round-trip correctness: verify top_logprobs is parsed as list[dict]
• Warning-free model_dump() with warnings-as-errors enabled
• Default None when field is absent

Summary

Added top_logprobs: List[Dict[str, float]] | None = None to LogprobsPart so that the field is fully typed, IDE-visible, and serializes without Pydantic warnings. Three regression tests cover the happy path, warning-free serialization, and the optional-field default.

Issue

Fixes #443

Local verification

$ PYTHONPATH=/tmp/together-python/src python -m pytest tests/unit/test_logprobs_type.py -v

============================= test session starts ==============================
platform linux -- Python 3.11.15, pytest-9.0.3, pluggy-1.6.0
rootdir: /tmp/together-python
configfile: pyproject.toml
collected 3 items

tests/unit/test_logprobs_type.py::test_logprobs_part_top_logprobs_is_list PASSED [ 33%]
tests/unit/test_logprobs_type.py::test_logprobs_part_model_dump_no_warning PASSED [ 66%]
tests/unit/test_logprobs_type.py::test_logprobs_part_top_logprobs_optional PASSED [100%]

$ PYTHONPATH=/tmp/together-python/src python -m pytest tests/unit/ -q

============ 6 failed, 177 passed, 14 warnings, 26 errors in 0.70s =============
(6 failures and 26 errors are pre-existing on upstream/main, confirmed by running
the same suite on the unpatched branch)

$ pre-commit run --files src/together/types/common.py tests/unit/test_logprobs_type.py

fix end of files.........................................................Passed
trim trailing whitespace.................................................Passed
check docstring is first.................................................Passed
check for merge conflicts................................................Passed
black....................................................................Passed
mypy.....................................................................Passed
=== LOCAL_TEST_PASSED ===

Risk

Purely additive type annotation — no runtime behaviour change. The field defaults to None, so all existing callers that don't use top_logprobs are unaffected. Users who do access response.choices[0].logprobs.top_logprobs already receive the correct list value (stored via extra="allow"); this PR simply makes the field explicit and statically typed.