Summary

/claim #290

This PR adds a focused AWS Comprehend PII redaction utility for the JS SDK:

• adds AWSComprehendRedactor with a Comprehend-compatible client interface
• supports direct text redaction for prompt strings and chat message content
• provides chainEndpoint() so existing endpoint-style chat() calls can be wrapped after redaction
• provides an Observable-like mapping helper for pipeline-style usage
• exports the redactor and related types from the AI package
• adds mocked Vitest coverage for redaction and endpoint chaining
• adds a Jsonnet-driven aws-comprehend-redaction example

Validation

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

Note: the example uses a mock Comprehend-compatible client so maintainers can run it without AWS credentials; production callers can pass a real AWS Comprehend adapter implementing detectPiiEntities().