- Cache grype binary using actions/cache to avoid repeated downloads
- Add retry logic (3 attempts with exponential backoff) for grype installation
- Pre-install grype before scan-action to ensure it's available
This addresses the HTTP 503/504 timeout errors when downloading grype from
GitHub releases, which caused 6 failures on the main branch in the past 14 days
(90.32% success rate vs 99% target).
db27c6763f