The content-addressed store — the on-disk half of assay, where the
"distro" actually lives. Blobs are keyed by their BLAKE3 hash, so:
- storing the same bytes twice dedups to one object (the density story), and
- a read is integrity-checked for free: if the bytes don't hash back to the key, the object is corrupt and the read fails.
No KVM here — this is plain filesystem work and is fully tested.