The class-killer for the lost-main.dkann incident (ADR-004 §7). A provider can
declare a derived-index blob FAMILY (a set of members that are load-bearing
together, e.g. vector-base = main.dkann + main.slotmap + main.slotrev). Once
declared:
- deleteBinaryBlob / removeRawPrefix REFUSE to remove a declared member, throwing
the new ProtectedArtifactError — an in-process GC / sweeper is now INCAPABLE of
deleting a load-bearing index file (COLD != DEAD). Intentional retirement is an
explicit unregisterDerivedFamily(name) first.
- The declaration persists to _system/derived-artifacts.json, so protection
survives a reopen; clear() resets it with the rest of the derived footprint.
- checkDerivedFamiliesPresent() names any member missing on open (the catch for an
EXTERNAL deleter that bypasses the in-process refusal) → rebuild from canonical.
- Transients (*.tmp.*, *.rebuild-tmp, *.rotate-tmp) are never protected; a
namespace family protects a growing prefix (seg-*).
New StorageAdapter surface (optional): registerDerivedFamily / unregisterDerivedFamily
/ listDerivedFamilies + DerivedFamilyDeclaration; new exported errors
ProtectedArtifactError / DerivedArtifactMissingError. Enforcement is inert until a
provider declares a family (no regression). Cor declares its 6 families + does the
atomic set-swap in 3.0.15 (M2); brainy builds the contract now. 8 tests.
