feat(beliefs): source reliability by domain, never global

A source's track record is kept per (evidence family, belief subject) and
updated only by outcomes: predictions derived from a belief resolving, and
operators marking a belief wrong. With three or more outcomes in a domain
the record adjusts the credibility of that source's new evidence in that
domain, and the adjustment is written on the evidence row. Standing in one
domain never moves standing in another, and the trust-level credibility
constants are never rewritten. Migration 0021 is additive; belief pages
show each cited family's record in the belief's domain.

internal/predictions/resolver.go

@@ -128,6 +128,9 @@ func (r *Resolver) ResolveIn(ctx context.Context, q storage.Querier, p Predictio
 			evs = append(evs, out[0])
 			return out[0], nil
 		}
+		if err := r.Beliefs.RecordBeliefOutcome(ctx, q, p.MindID, p.BeliefID, o.Status == StatusConfirmed); err != nil {
+			r.Log.Warn("reliability update failed", "belief", p.BeliefID, "err", err)
+		}
 		if _, err := r.Beliefs.AddEvidence(ctx, q, emit, p.MindID, p.BeliefID, beliefs.EvidenceInput{Direction: dir, Kind: "prediction", RefID: string(p.ID), Source: "prediction:" + string(p.ID), Weight: weight, Credibility: 0.9, Note: "prediction " + string(o.Status) + ": " + p.Statement,
 			Derivation: beliefs.DerivationPrediction, Family: "prediction:" + string(p.ID), RootIDs: refIDs(o.Evidence)}, "prediction "+string(o.Status), evs[0].ID, ids.Nil); err != nil {
 			r.Log.Warn("belief feedback failed", "belief", p.BeliefID, "err", err)