Add AWS Comprehend PII redaction utility

[alceops]

Closes #290

Summary

• add AwsComprehendRedactor utility for AWS Comprehend DetectPiiEntities
• support AWS SDK v2-style detectPiiEntities() clients and SDK v3 send() clients via a command factory
• add score/type filtering, custom replacement tokens, entity metadata return, README usage, and Jest coverage

Verification

• npm run build
• npx jest src/ai/src/tests/awsComprehendRedactor.test.ts --runInBand

[alceops]

Quick verification/update: this PR is still mergeable and the visible checks are green. Local verification from JS/edgechains/arakoodev was npm run build plus npx jest src/ai/src/tests/awsComprehendRedactor.test.ts --runInBand passing. If there are style/API-shape changes you want for the AWS Comprehend redactor before review, I can turn them around quickly.