Add Opus 4.5 and 4.1 model types, use Opus 4.5 in poe
Update ocaml-claudeio bindings with new Opus model variants from the
Python SDK: Opus_4_5 (claude-opus-4-5) and Opus_4_1 (claude-opus-4-1).
Switch poe bot to use Opus 4.5 for both message handling and changelog
generation.
Co-Authored-By: Claude Opus 4.5 <noreply@anthropic.com>