Safe screenshot retries with idempotency keys.

Implementation checklist

• Use one key per release, locale matrix, and render spec.
• Include the commit SHA or release tag.
• Reuse the same key on network retries.
• Change the key when the render spec intentionally changes.

Recommended key shape

A practical key is release-42-ios-en-us or ${GITHUB_SHA}-store-screenshots. The point is stable identity for the work, not randomness.