Add AWS Comprehend PII redaction utility

[VexCode24]

Fixes #290
/claim #290

Summary

• add AwsComprehendRedactor to the AI package, backed by Amazon Comprehend DetectPiiEntities
• support redacting plain prompts, chat message arrays, and calling existing chat endpoints after redaction
• include a runnable AWS Comprehend + OpenAI example under examples/aws-comprehend-redaction

Tests

• node node_modules/vitest/vitest.mjs run src/ai/src/tests/awsComprehendRedactor.test.ts
• node node_modules/typescript/bin/tsc -b

[github-actions]

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