Add AWS Comprehend PII redaction helper

[MulaNele]

Summary:

• Adds ComprehendRedactor to the JS SDK AI package using @aws-sdk/client-comprehend.
• Supports direct PII detection/redaction, wrapChat() for existing LLM endpoints, and Observable-style subscribe() / pipe() helpers for chainable redaction flows.
• Exports the helper and related option/result/observable types from @arakoodev/edgechains.js/ai.
• Adds mocked Vitest coverage under src/ai/src/testcases/comprehend, including direct redaction, endpoint wrapping, and Observable-style chaining.
• Adds an aws-comprehend-redaction example with AWS environment setup notes.

Verification:

• node node_modules\vitest\vitest.mjs run src/ai/src/testcases/comprehend/comprehendRedactor.test.ts — 7 tests passed
• node node_modules\typescript\bin\tsc --noEmit --target ES2022 --module NodeNext --moduleResolution NodeNext --esModuleInterop --strict --skipLibCheck --types node src/ai/src/lib/comprehend/comprehendRedactor.ts src/ai/src/testcases/comprehend/comprehendRedactor.test.ts
• node node_modules\prettier\bin\prettier.cjs --check src/ai/src/lib/comprehend/comprehendRedactor.ts src/ai/src/testcases/comprehend/comprehendRedactor.test.ts src/ai/src/index.ts README.md ../examples/aws-comprehend-redaction/src/index.ts ../examples/aws-comprehend-redaction/README.md ../examples/aws-comprehend-redaction/package.json ../examples/aws-comprehend-redaction/tsconfig.json
• git diff --check

Note:

• Full project typecheck currently hits pre-existing repo issues unrelated to this change, including src/document-loader/src/lib/pdf-loader/pdfLoader.ts missing pdf-parse/lib/pdf-parse.js types and existing implicit-any errors in older AI modules.

/claim #290

[github-actions]

CLA Assistant Lite bot All contributors have signed the CLA ✍️ ✅

[MulaNele]

Implementation notes for reviewers:

• Adds an AWS Comprehend-based redaction utility using the official @aws-sdk/client-comprehend package.
• Supports direct text redaction, prompt option redaction, chat wrapper usage, and Observable-style subscribe/pipe helpers for chainable workflows.
• Includes mocked unit coverage for entity detection, redaction, chat wrapping, observable helpers, and error propagation.
• Adds a runnable example under examples/aws-comprehend-redaction.

[MulaNele]

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

[MulaNele]

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