Two known-degraded states were recorded but never consulted by the read paths, so
a partial result looked authoritative:
- commitSingleOp returns `degraded` ids on an adopt-forward failed-rollback
recovery (the canonical record is durable but its derived-index entry may be
incomplete). persistSingleOp dropped that list on the floor — no health flag,
no read signal. It now records them in a queryable degraded set.
- A non-fatal index-rebuild failure at init (_indexRebuildFailed) was folded into
checkHealth()/validateIndexConsistency() but no read consulted it.
find() and get() now emit ONE loud warning per degraded window (reads still
return — canonical is the source of truth — but the caller is told results may be
partial and to run repairIndex()). Both degraded sources fold into the two health
surfaces, and repairIndex() reconciles from canonical and clears them.
