Update the alert digest wording

internal/briefing/base_modules_test.go

@@ -367,6 +367,39 @@ func TestAlertDigestDistinguishesCheckedEmptyAndMissing(t *testing.T) {
 	}
 }
 
+func TestAlertDigestIncludesPeriodAndGuidance(t *testing.T) {
+	registry := MustDefaultModuleRegistry()
+	ctx := testModuleContext()
+	ctx.Collected.Alerts = &weatherdata.AlertRun{Alerts: []json.RawMessage{json.RawMessage(`{"event":"Wind Advisory"}`)}}
+	ctx.Derived.AlertOverlaps = []forecast.AlertOverlap{{
+		Event:       "Wind Advisory",
+		Headline:    "Wind Advisory until 8 PM",
+		Severity:    "Moderate",
+		Period:      timeutil.Period{Start: mustParseModuleTime("2026-06-17T18:00:00Z"), End: mustParseModuleTime("2026-06-18T01:00:00Z")},
+		Instruction: "Secure outdoor objects.",
+		Description: "Gusty winds may blow around unsecured objects.",
+	}}
+
+	output, err := registry.BuildModule(ctx, module.ConfigItem{ID: module.AlertDigest})
+	if err != nil {
+		t.Fatalf("BuildModule(alert digest) error = %v", err)
+	}
+	value := moduleValue[AlertDigestModule](t, output)
+	if len(value.Relevant) != 1 {
+		t.Fatalf("Relevant length = %d, want 1", len(value.Relevant))
+	}
+	alert := value.Relevant[0]
+	if alert.Event != "Wind Advisory" || alert.Headline != "Wind Advisory until 8 PM" || alert.Severity != "Moderate" {
+		t.Fatalf("alert identity = %#v, want preserved event/headline/severity", alert)
+	}
+	if alert.PeriodBegins != "June 17 at 1:00 PM" || alert.PeriodEnds != "June 17 at 8:00 PM" {
+		t.Fatalf("alert period = %q/%q, want friendly local labels", alert.PeriodBegins, alert.PeriodEnds)
+	}
+	if alert.Instruction != "Secure outdoor objects." || alert.Description != "Gusty winds may blow around unsecured objects." {
+		t.Fatalf("alert guidance = %#v, want instruction and description preserved", alert)
+	}
+}
+
 func TestBaseModulesOmitMissingOptionalOutputs(t *testing.T) {
 	registry := MustDefaultModuleRegistry()
 	ctx := testModuleContext()