GeezerVison

This adds an artifact-retention-days input to the build and bake reusable workflows so callers can control how long uploaded local build artifacts are retained.

The new input defaults to 0, which preserves the current repository default retention behavior. This matters for large artifacts because local build outputs can consume a lot of GitHub artifact storage when they keep the default retention window. Letting callers shorten retention is a practical way to reduce storage pressure and cost for short-lived CI artifacts, while still allowing longer retention when artifacts need to support release, audit, or debugging workflows.