feat(report): close v2 headline and coverage gaps

scripts/report_event_coverage_test.go

@@ -0,0 +1,29 @@
+//go:build llm_script
+
+package main
+
+import "testing"
+
+func TestParseCoverageArgsRejectsReverseRange(t *testing.T) {
+	if _, _, err := parseCoverageArgs("2026-05-14", "2024-06-01"); err == nil {
+		t.Fatalf("expected reverse range to fail")
+	}
+}
+
+func TestSummarizeCoverageCalculatesPercent(t *testing.T) {
+	summary := summarizeCoverage([]CoverageDay{
+		{Date: "2024-06-05", OfficialRelease: true},
+		{Date: "2024-10-25", PromoCampaign: true},
+		{Date: "2026-05-14"},
+	})
+
+	if summary.TotalDays != 3 {
+		t.Fatalf("total days = %d, want 3", summary.TotalDays)
+	}
+	if summary.CoveredDays != 2 {
+		t.Fatalf("covered days = %d, want 2", summary.CoveredDays)
+	}
+	if summary.CoveragePct < 66.6 || summary.CoveragePct > 66.7 {
+		t.Fatalf("coverage pct = %.2f, want about 66.67", summary.CoveragePct)
+	}
+}