chore: type improvements related to select_streaming_callback overloads

[anakin87]

Related Issues

• in chore: improve select_streaming_callback type hints haystack#9513, I tried to improve type hints for select_streaming_callback, adding overloads variants
• nightly failure in Bedrock https://github.com/deepset-ai/haystack-core-integrations/actions/runs/15915262271/job/44891617591
  • this failure stems from the fact that mypy is not able to understand that overloading a bool parameter with 2 variants (Literal[True] and Literal[False]) is exhaustive. See (🐞) overloads that exhaust finite Literals(bool/Enum) not treated as exhaustive python/mypy#14764.

Proposed Changes:

• Bedrock: ignore this type error
• Cohere and Anthropic: remove type: ignore thanks to the overloads introduced

How did you test it?

CI

Checklist

• I have read the contributors guidelines and the code of conduct
• I have updated the related issue with new insights and changes
• I added unit tests and updated the docstrings
• I've used one of the conventional commit types for my PR title: fix:, feat:, build:, chore:, ci:, docs:, style:, refactor:, perf:, test:.

[sjrl]

Thanks!