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

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