Versioned reusable action for App Store and TestFlight IPA decrypts. It verifies downloaded IPA SHA-256 and size, retries transient requests, emits resolved build/channel/cache outputs, and supports latest TestFlight builds and existing artifact downloads. Pin consumers to castdrian/dkrypt/.github/actions/dkrypt-decrypt@v1.0.0; the major tag v1 tracks this release.