A Merkle-style digest summarizes the derived tier (per-identity fingerprint +
incident edges as order-independent leaves) so equal states have equal digests
and the digest is stable under equivalent event orders. A ConsistencyChecker
recomputes the authoritative fold from the current source, compares it over a
sampled region, and on mismatch scoped-recomputes just the affected identities —
self-healing missed-delta drift, corrupted internal state, and vanished pages.
Makes derived = f(canonical) verified, not asserted.
Co-Authored-By: Claude Opus 4.8 <noreply@anthropic.com>