amipkg 0.5.7

Hardening after an adopt-then-upgrade incident: (1) adopting amipkg at its own drawer no longer inventories cache/db/config, trace files, or the catalog - the upgrade's remove-previous step deleted the receipt DB and the freshly extracted files mid-upgrade, leaving 'nothing installed'. (2) amipkg's runtime state (cache/db/config) is NEVER deleted through a receipt, whatever a receipt claims. (3) An empty extraction now aborts BEFORE anything is removed - a failed unpack can no longer destroy the installed version. Also pins the versioned release URL (no more sha mismatch when a new release lands before your catalog update).