feat(bedrock): add guardrail_last_turn_only option

[JackYPCOnline]

Description

This PR is a clean up based on #1224 that resolve #999

Also fix Lint error.

Related Issues

#1224

Documentation PR

Type of Change

Bug fix
New feature
Breaking change
Documentation update
Other (please describe):

Testing

How have you tested the change? Verify that the changes do not break functionality or introduce warnings in consuming repositories: agents-docs, agents-tools, agents-cli

• [x ] I ran hatch run prepare

Checklist

• [x ] I have read the CONTRIBUTING document
• [x ] I have added any necessary tests that prove my fix is effective or my feature works
• [x ] I have updated the documentation accordingly
• [x ] I have added an appropriate example to the documentation to outline the feature, or no new docs are needed
• [x ] My changes generate no new warnings
• [x ] Any dependent changes have been merged and published

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Codecov Report

✅ All modified and coverable lines are covered by tests.

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