fix(ci): report a cell that never ran a test as failed, not clean (#614)

Render summed FailCount across suites and printed "No failures across any
suite" whenever the total was zero, without asking whether any test had run.

A cell that dies during provisioning emits junit with no testcases at all, so
it took the clean path. Nightly run 30467638631 cell 20 failed with "install
callback never fired after 3 attempts; PXE never triggered install" and its
analysis.md read "No failures across any suite" — absence of evidence rendered
as positive evidence.

Zero testcases now renders a warning naming the layer above the suites. A run
with tests and no failures is unchanged.

.github/actions/e2e-analyze/analyze.go

@@ -467,9 +467,19 @@ func Render(r Report) string {
 	var b strings.Builder
 	fmt.Fprintf(&b, "## %s\n\n", r.Title)
 
-	totalFail := 0
+	totalFail, totalTests := 0, 0
 	for _, s := range r.Suites {
 		totalFail += s.FailCount
+		totalTests += s.Total
+	}
+
+	// A cell that dies before the suites run emits junit with no testcases at
+	// all. Reporting that as clean turns "nothing ran" into "nothing wrong", so
+	// name it and point above the suites.
+	if totalTests == 0 {
+		b.WriteString("⚠️ No tests ran — no testcases in any junit file. " +
+			"The failure is upstream of the suites (provisioning, bootstrap, or reimage); check the job log.\n")
+		return b.String()
 	}
 	if totalFail == 0 {
 		b.WriteString("✅ No failures across any suite.\n")

.github/actions/e2e-analyze/analyze_test.go

@@ -189,3 +189,25 @@ func TestRender_NoFailuresIsClean(t *testing.T) {
 		t.Errorf("expected zero-failure banner, got:\n%s", out)
 	}
 }
+
+// A cell that fails in provisioning writes junit with no testcases. Rendering
+// the clean banner there reports "nothing ran" as "nothing wrong".
+func TestRender_NoTestsRanIsNotClean(t *testing.T) {
+	for _, tc := range []struct {
+		name   string
+		suites []SuiteReport
+	}{
+		{"empty junit file", []SuiteReport{{File: "junit-baremetal.xml", Label: "baremetal", Total: 0, FailCount: 0}}},
+		{"no junit files at all", nil},
+	} {
+		t.Run(tc.name, func(t *testing.T) {
+			out := Render(Report{Title: "E2E failure analysis", Suites: tc.suites})
+			if strings.Contains(out, "No failures across any suite") {
+				t.Errorf("clean banner rendered when no test ran, got:\n%s", out)
+			}
+			if !strings.Contains(out, "No tests ran") {
+				t.Errorf("expected a no-tests-ran warning, got:\n%s", out)
+			}
+		})
+	}
+}