Download and delta

Do not cross-decode: KVDIFFHP1, HDIFF13&, BSDIFF40, VCDIFF D6 C3 C4. Unknown magic → full package. Unknown admin algo → DELTA_ALGO_UNSUPPORTED. Failed delta Jobs: bell / JOB_FAILED.

Multi-file pack oversize is 200 full_package, not 400. Client pack has no admin job_id. local_sha256 exists only on diff. Downloads are /packages/{sha256}, not /artifacts/{id}/{filename}.