* fix(responses): drop the null created_by OpenAI rejects when output items are replayed
* fix(responses): drop a null created_by from replayed input items too
A conversation saved from an older proxy still carries created_by: null on its compaction, apply_patch and shell items, so OpenAI keeps rejecting the replay. Drop the null from input items on the HTTP request transform and the WebSocket response.create rewrite, keeping a created_by that is not null.
* fix(responses): drop a null created_by from counted input items too
* test(responses): cover saved reasoning nulls and re-compaction of a saved conversation
* fix(responses): drop a set created_by from input under drop_params
* fix(types): type the Responses output serializer's parameters
* fix(responses): drop a set created_by on reasoning items and Perplexity presets under drop_params
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Co-authored-by: mateo-berri <277851410+mateo-berri@users.noreply.github.com>
