Clarify configuration evidence providers

docs/consumers/guide.md

@@ -253,6 +253,9 @@ owns operator syntax and report details. `Scope.Features` declares optional mode
 `View.Metadata` and `View.Findings` carry native path metadata and diagnostic
 records when available. `Findings.Messages` contains presentations associated
 with those records, while `Acquired.Diagnostics` carries independent messages.
+Custom explanation providers implement `Explain`; CommandKit renders the
+acquired evidence. See `EffectiveWriter` and `ExplanationReader` in the
+[ckconfig GoDoc](../../integrations/ckconfig/contracts.go) for the provider boundary.
 Set `Scope.Features.Overrides` only when the loader passes
 `Selection.Overrides` to ConfigKit as part of its normal load. The integration
 parses CLI records but cannot add them to an already-loaded result. The