The log group already exists — created by the compute stack's
logRetention setting on the suggestions Lambda. Adding it to the
foundation stack caused a duplicate resource error on deploy.
oss-index-creator Lambda was missing functionName, arm64 architecture,
and explicit log retention — all required by the engineering handbook.
CI workflow was not passing node-version to reusable workflows, risking
drift. Removed unused _api_request helper from all four main Lambdas.
Added missing suggestions log group to foundation stack.