Add AWS Comprehend PII redactor

[Simultech369]

Summary

• Add a ComprehendRedactor utility for AWS Comprehend-style PII redaction
• Support simple detectPiiEntities(input) clients and AWS SDK v3-style send(command) clients via command factories
• Add configurable language code, replacement behavior, and minimum confidence filtering
• Export the utility from the AI package
• Add tests for redaction, confidence filtering, custom replacements, and SDK-v3 style usage

Closes #290

Test Plan

• npx.cmd vitest run comprehendRedactor
• npx.cmd tsc -b
• git diff --check

[github-actions]

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[Simultech369]

I have read the Arakoo CLA Document and I hereby sign the CLA

[Simultech369]

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[Simultech369]

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[Simultech369]

/claim #290

[Simultech369]

I am cleaning up older open PRs on my account. If this #290 PII-redactor slice is still reviewable or eligible, I am happy to keep it open and make changes.

Otherwise, I will close it after a short grace period to reduce queue noise.

[Simultech369]

Updated this PR to fulfill all acceptance criteria for #290:

• Added ComprehendRedactorEndpoint allowing automatic chaining with existing EdgeChains AI endpoints (OpenAI, GeminiAI, LlamaAI, or any chat endpoint) via redactor.chain(endpoint).
• Added reactive SimpleObservable stream support via redactor.observe(prompt) and observeAndChat() for stream pipelines.
• Added comprehensive unit tests covering prompt & message redaction chaining and observable streaming.
• Added a full runnable working example in JS/edgechains/examples/aws-comprehend-redactor/ with complete documentation.

Ready for review and merge @sandys!
Payout address (Base USDC): 0xEa3A353Fb3fc88DB8F0FA1E6Ea541FEdc9F5F0E7