feat(generative): expose frequency_penalty on the Cohere runtime config

[Anai-Guo]

What

GenerativeConfig.cohere() (the query-time runtime config) exposes presence_penalty but has no frequency_penalty, so there is no way to set Cohere's frequency penalty from the v4 Python client.

The field exists everywhere else in the stack:

• Proto — GenerativeCohere in weaviate/proto/v1/v6300/v1/generative_pb2.pyi declares frequency_penalty (right next to presence_penalty).
• Server — modules/generative-cohere/parameters/params.go parses frequencyPenalty into Params.FrequencyPenalty, and modules/generative-cohere/clients/cohere.go:104 forwards it to Cohere as frequency_penalty.
• Other providers — every provider whose proto message carries both penalties exposes both in this file: databricks, deepseek, google, openai. Cohere is the only place where the pair is split.

So the gap is purely on the client side: _GenerativeCohere never declared the field, and _to_grpc never populated it.

Change

• Add frequency_penalty: Optional[float] to _GenerativeCohere.
• Pass it through _GenerativeCohere._to_grpc.
• Add the frequency_penalty keyword (plus docstring line) to the cohere() factory.

7 added lines, nothing removed — no behaviour change for callers that don't pass the new keyword, since it defaults to None and stays unset on the proto message.

Test

Extended the existing cohere case in test/collection/test_classes_generative.py to set frequency_penalty=0.4 and assert it lands on the GenerativeCohere message.

Verified against a clean checkout of main (ae327ca):

# with the library change reverted, test kept:
ERROR test/collection/test_classes_generative.py - TypeError: GenerativeConfig.cohere() got an unexpected keyword argument 'frequency_penalty'

# with the change:
20 passed, 2 warnings in 0.23s

Full unit suite: 384 passed, 1 skipped, 2 failed. The two failures are test/test_timeout.py::test_timeout_prints_test_name_and_stacktrace and ::test_timeout_with_passing_and_hanging_test, which fail identically on unmodified main — unrelated to this change.

Lint: ruff==0.14.7 (the pin in requirements-devel.txt) — check clean, format --check reports both files already formatted.

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[orca-security-eu]

Orca Security Scan Summary

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