fix(control-plane): discard malformed SQS messages

[edersonbrilhante]

Description

Treat malformed SQS message bodies as permanent, non-retryable failures. The scale-up handler logs and acknowledges malformed records so they do not block valid messages in the same batch or repeatedly return to the queue.

Document the SQS event source mapping contract near batchItemFailures and update the focused handler tests for the new behavior.

Test Plan

1. Send a scale-up SQS batch containing one valid message and one malformed JSON body.
2. Confirm the valid message is passed to scaleUp.
3. Confirm the malformed message is logged but omitted from batchItemFailures.
4. Confirm a message rejected by scaleUp is still returned in batchItemFailures.
5. Run yarn vitest run functions/control-plane/src/lambda.test.ts --config functions/control-plane/vitest.config.ts --reporter=dot.

Related Issues

None.

[github-actions]

Dependency Review

✅ No vulnerabilities or license issues or OpenSSF Scorecard issues found.

Scanned Files

None