Validate Distributor endpoints before publication

internal/app/batch_generation_test.go

@@ -61,6 +61,29 @@ func TestRunBatchDetailedNotifiesOnlyAfterAllOutputsExist(t *testing.T) {
 	}
 }
 
+func TestRunBatchDetailedRejectsUnsupportedDistributorEndpointBeforeWork(t *testing.T) {
+	outputDir := t.TempDir()
+	cfg := generationDistributorConfig()
+	cfg.Notify.Distributor.Endpoint = "ftp://distributor.example.test"
+	bundle := generationBundle(t)
+	collector := &generationCollector{bundle: &bundle}
+	executor := &generationExecutor{}
+	notifier := &generationNotifier{}
+
+	result, err := RunBatchDetailed(context.Background(), BatchRequest{
+		Config: cfg, Batch: BatchMorning,
+		Now: generationTime("2026-05-29T08:30:00-05:00"), WorkingDir: t.TempDir(), OutputDir: outputDir,
+		Collector: collector, Executor: executor, Notifier: notifier,
+	})
+	if err == nil || result != nil || collector.called || executor.promptInspections != 0 || executor.called || notifier.calls != 0 || notifier.batchCalls != 0 {
+		t.Fatalf("RunBatchDetailed() result/error/collector/executor/notifier = %#v/%v/%t/%#v/%#v", result, err, collector.called, executor, notifier)
+	}
+	entries, readErr := os.ReadDir(outputDir)
+	if readErr != nil || len(entries) != 0 {
+		t.Fatalf("output directory entries/error = %v/%v", entries, readErr)
+	}
+}
+
 func TestRunBatchDetailedUsesDefaultAndConfiguredOutputDirectories(t *testing.T) {
 	tests := []struct {
 		name      string