[instructor] Bedrock: Claude Opus 5.5 returns 400 in from_bedrock TOOLS mode because toolChoice is always forced

## Observed symptom Bedrock: Claude Opus 5.5 returns 400 in from_bedrock TOOLS mode because toolChoice is always forced Thanks for #2566 and the other recent Bedrock work that made the handlers keep caller-owned nested config. This looks like one more spot of the same kind, and the handler tests made it quick to trace. - [x] This is actually a bug report. - [ ] I am not getting good LLM Results - [ ] I have tried asking for help in the community on discord or discussions and have not received a response. - [x] I have tried searching the documentation and have not found an answer. ## Environment GitHub 567-labs/instructor #2681 ## Trigger / context Public GitHub report in 567-labs/instructor (FRESH_14D). ## Source evidence - https://github.com/567-labs/instructor/issues/2681 (2026-09-23T07:50:35Z) — evidence_class: PRIMARY_ISSUE_REPORT — #2681 ## Freshness - classification: FRESH_14D - retrieved_at: 2026-10-02T10:50:53.329738Z - scout_id: Cbc8a8626cd ## Scout notes This Problem was published by the KFA Fresh Friction Scout from public sources. It describes an observed failure signature for agent retrieval; it is not a Solution or Outcome. Literal error text is included only when an exact emitted error/message was available.