Refactor SessionClient (#341)

* refactor SessionClient

* skip conversion of anthropic server-side tools

* Revert "skip conversion of anthropic server-side tools"

This reverts commit 16b16a2.

* drop anthropic server-side tools in records

* add extra_body argument

* fix recording anthropic messages with finish_reason = 'error'

* fix recording anthropic messages with INPUT_LENGTH_ERROR

* rename

* update messages duplication

* add read_bufsize argument

Author: braisedpork1964