Document smoke-test diagnostics

docs/consumers/pkg-promptkit.md

@@ -216,6 +216,69 @@ request-specific overrides. An empty diff is not proof of equivalent execution.
 Records can contain ordinary application data, so use the application's
 disclosure policy when presenting them.
 
+## Run Explicit Smoke Diagnostics
+
+[`Engine.SmokeTest`](../../smoke_diagnostics.go) runs one explicit diagnostic
+using a target resolved from the engine's captured configuration. It does not
+execute the selected application prompt or its inputs, session, artifacts, or
+output schema. Unlike the offline examples and default test suite, calling it
+can contact the selected provider and use configured credentials. It is a
+consumer operation, not an automatic readiness verdict or a release check.
+
+For example, a caller can request the built-in text inference check and treat
+its optional fact as an observation rather than assuming that a nil Go error
+means success:
+
+```go
+report, err := engine.SmokeTest(ctx, promptkit.SmokeTestRequest{
+	Kind:      promptkit.SmokeTestTextInference,
+	ProfileID: profileID,
+	APIKey:    apiKey,
+})
+if err != nil {
+	if report != nil {
+		retainDisclosureSafeSummary(report)
+	}
+	return err
+}
+if report != nil {
+	matched := report.Facts.ExpectedTextMatched
+	switch {
+	case matched == nil:
+		// The comparison was not evaluated or is unknown/inapplicable.
+	case *matched:
+		// The private expected-text comparison matched.
+	default:
+		// It did not match; the operation may still have concluded normally.
+	}
+}
+```
+
+A nil Go error means the diagnostic concluded, not that its finding was
+positive. Fact pointers are tri-state: nil means unknown, not evaluated, or
+inapplicable. Reports contain factual observations and effective settings, not
+generated text or provider bodies; identifiers and settings can still be
+sensitive. The
+[`SmokeTest` GoDoc](../../smoke_diagnostics.go) owns selection precedence,
+exact fields, timeout and retry behavior, supported transports, and disclosure
+details.
+
+Caller cancellation can return both an error and a partial report. Preserve the
+context error identity and inspect any available observations before returning:
+
+```go
+report, err := engine.SmokeTest(ctx, request)
+if report != nil {
+	retainDisclosureSafeSummary(report)
+}
+if err != nil {
+	if errors.Is(err, context.Canceled) || errors.Is(err, context.DeadlineExceeded) {
+		// The report may describe work completed before interruption.
+	}
+	return err
+}
+```
+
 ## Inspect A Prompt Before Preparation
 
 Use [`Engine.InspectPrompt`](../../engine.go) to check one configured prompt's