Generalize distributor report path rendering

internal/app/app_test.go

@@ -2214,6 +2214,55 @@ func TestResolveGenerateStorm(t *testing.T) {
 	}
 }
 
+func TestDistributorTemplateValuesDeriveStormID(t *testing.T) {
+	cfg := config.Defaults()
+	cfg.WeatherAPI.Timezone = "America/Chicago"
+	now := mustParse("2026-05-29T12:00:00-05:00")
+	start := mustParse("2026-05-29T18:00:00-05:00")
+	end := mustParse("2026-05-30T06:00:00-05:00")
+
+	resolved, err := ResolveGenerate(GenerateRequest{
+		Config:     cfg,
+		Report:     ReportStorm,
+		StormStart: start,
+		StormEnd:   end,
+	}, now)
+	if err != nil {
+		t.Fatalf("ResolveGenerate() error = %v", err)
+	}
+	values, err := distributorTemplateValuesForReport(cfg, resolved, "run", "")
+	if err != nil {
+		t.Fatalf("distributorTemplateValuesForReport() error = %v", err)
+	}
+	if values.StormID != "2026-05-29T1800-2026-05-30T0600" {
+		t.Fatalf("StormID = %q, want storm valid-period stamp", values.StormID)
+	}
+}
+
+func TestDistributorTemplateValuesLeaveStormIDEmptyForOtherReports(t *testing.T) {
+	cfg := config.Defaults()
+	cfg.WeatherAPI.Timezone = "America/Chicago"
+	location, err := timeutil.LoadLocation(cfg.WeatherAPI.Timezone)
+	if err != nil {
+		t.Fatalf("load location: %v", err)
+	}
+	resolved, err := report.Resolve(report.Today, report.ResolveRequest{
+		Now:      mustParse("2026-05-29T12:00:00-05:00"),
+		Location: location,
+	})
+	if err != nil {
+		t.Fatalf("Resolve() error = %v", err)
+	}
+
+	values, err := distributorTemplateValuesForReport(cfg, resolved, "run", "")
+	if err != nil {
+		t.Fatalf("distributorTemplateValuesForReport() error = %v", err)
+	}
+	if values.StormID != "" {
+		t.Fatalf("StormID = %q, want empty for %s", values.StormID, resolved.Definition.ID)
+	}
+}
+
 func TestBatchRunIDUsesUTCStartAndBatchName(t *testing.T) {
 	tests := []struct {
 		name      string