resolveImage maps placement.image to a configured key or URL; imageCache
streams the download through StorageVolUpload with a sha256 tee, writes
a marker volume when the upload is verified, and re-fetches when the
marker is missing or the configured checksum changed. Errors carry
taxonomy sentinels that classify now honours. Adds the in-memory fake
libvirt API used from here on.
Step 3b of docs/plans/2026-09-04-1404-kvm-provider.md.
Co-Authored-By: Claude Fable 5.1 <noreply@anthropic.com>
