Fix LLMConfig for 5 notebooks (7)

[0xfandom]

Why are these changes needed?

Continues the migration from dict-based llm_config / config_list_from_json to the typed LLMConfig API across the example notebooks. Sequence (7) following #2782.

Notebooks updated:

• notebook/agentchat_human_feedback.ipynb
• notebook/agentchat_planning.ipynb
• notebook/agentchat_stream.ipynb
• notebook/agentchat_teachability.ipynb
• notebook/agentchat_websockets.ipynb

Each one now uses autogen.LLMConfig(...) or autogen.LLMConfig.from_json(...).where(...) and passes the resulting object directly to agents instead of a dict containing config_list. Where filter dicts were used, they are now expressed via .where(model=...).

Related issue number

Refs #1394

Checks

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• I've added tests (if relevant) corresponding to the changes introduced in this PR.
• I've made sure all auto checks have passed.

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• I understand the changes in this PR and can explain them in my own words.
• I have verified that the PR description accurately reflects the actual diff.

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Codecov Report

✅ All modified and coverable lines are covered by tests.
see 57 files with indirect coverage changes

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