Add X-Ray SDK instrumentation to Lambda aggregator

Summary

The Lambda aggregator function needs X-Ray SDK instrumentation to capture DynamoDB subsegments in traces.

Background

Issue #107 Phase 1 added X-Ray tracing infrastructure:

• TracingConfig.Mode: Active on Lambda
• Conditional X-Ray IAM permissions
• enable_tracing flag in StackOptions/CLI

However, Lambda invocations are traced but DynamoDB calls are not captured as subsegments because the aggregator uses plain boto3 without X-Ray SDK patching.

Proposed Solution

1. Add aws-xray-sdk to Lambda dependencies
2. Patch boto3 in the Lambda handler:

   from aws_xray_sdk.core import patch_all
   patch_all()
   

3. Update lambda_builder.py to include the X-Ray SDK in the deployment package

Impact

• Lambda deployment package size will increase
• DynamoDB calls will appear as subsegments in X-Ray traces
• Enables end-to-end tracing visibility

Related

• Parent: #107 (AWS X-Ray Tracing Integration)
• Prerequisite: May require changes to how Lambda packages are built

Start by reading lambda_builder.py and locating the Lambda aggregator handler, then inspect how its dependencies are assembled. Add the aws-xray-sdk dependency and verify that DynamoDB calls from the packaged Lambda appear as X-Ray subsegments while the existing deployment packaging still works.