Harden diagnostic handling and warning presentation

internal/cli/state_hardening_test.go

@@ -868,6 +868,7 @@ type stateTestHarness struct {
 	sessionIDs               []string
 	outputDiagnostics        contracts.DiagnosticCollection
 	includeWarnings          bool
+	includeWarningFile       bool
 }
 
 func newStateTestHarness() *stateTestHarness { return &stateTestHarness{} }
@@ -1012,7 +1013,11 @@ func (o stateTestOutput) Encode(_ context.Context, req contracts.OutputRequest)
 	if o.includeDiagnostics && len(req.Diagnostics.Groups) > 0 {
 		data = []byte(fmt.Sprintf("{\"ok\":true,\"diagnostics\":%q}\n", req.Diagnostics.Groups[0].ReasonCode))
 	}
-	return contracts.OutputResult{Files: []contracts.OutputFile{{Name: "result.json", Bytes: data}}}, nil
+	files := []contracts.OutputFile{{Name: "result.json", Bytes: data}}
+	if o.harness.includeWarningFile {
+		files = append(files, contracts.OutputFile{Name: "warnings.json", Bytes: []byte("{\"warnings\":true}\n")})
+	}
+	return contracts.OutputResult{Files: files}, nil
 }
 
 func stateTestDiagnostic(scope, reasonCode, message string) contracts.ProducerDiagnostic {