ui(relTime): tick relative timestamps client-side so long-open tabs don't freeze

formatRelTime now wraps its label in <time data-rel-ts=...>, and
both layouts include a small ticker that re-renders every 30s.
Without this, a job-detail page rendered an hour ago kept showing
'2h ago' when the wall-clock truth was '3h ago'.

internal/server/ui/funcs.go

@@ -221,23 +221,40 @@ func formatBytes(n int64) template.HTML {
 // "in 5m"-style. Accepts *time.Time or time.Time so templates can
 // pass either without fighting Go's lack of an address-of operator.
 // Anything else returns "—".
-func formatRelTime(v any) string {
+//
+// The output is wrapped in a <time data-rel-ts="..."> element so a
+// small client-side ticker (see base.html) can refresh the label
+// without a full page reload — otherwise a long-open tab shows
+// timestamps frozen at render time.
+func formatRelTime(v any) template.HTML {
 	var t time.Time
 	switch x := v.(type) {
 	case time.Time:
 		t = x
 	case *time.Time:
 		if x == nil {
-			return "—"
+			return template.HTML("—")
 		}
 		t = *x
 	default:
-		return "—"
+		return template.HTML("—")
 	}
 	if t.IsZero() {
-		return "—"
+		return template.HTML("—")
 	}
-	d := time.Since(t)
+	label := relTimeLabel(time.Since(t))
+	return template.HTML(fmt.Sprintf(
+		`<time data-rel-ts="%s" title="%s">%s</time>`,
+		t.UTC().Format(time.RFC3339Nano),
+		t.UTC().Format("2006-01-02 15:04:05 UTC"),
+		label,
+	))
+}
+
+// relTimeLabel turns a duration-since-now into the short human label
+// used by formatRelTime (and mirrored verbatim by the JS ticker, so
+// keep the two in sync if you change the buckets).
+func relTimeLabel(d time.Duration) string {
 	suffix := "ago"
 	if d < 0 {
 		d = -d

internal/server/ui/funcs_test.go

@@ -0,0 +1,49 @@
+package ui
+
+import (
+	"strings"
+	"testing"
+	"time"
+)
+
+func TestFormatRelTimeWrapsInTickableTimeElement(t *testing.T) {
+	// A long-open tab needs a stable anchor so the JS ticker can
+	// refresh the label — see base.html.
+	when := time.Now().Add(-3 * time.Hour)
+	got := string(formatRelTime(when))
+	if !strings.Contains(got, `<time data-rel-ts="`) {
+		t.Errorf("missing data-rel-ts anchor in %q", got)
+	}
+	if !strings.Contains(got, "3h ago</time>") {
+		t.Errorf("expected '3h ago' label, got %q", got)
+	}
+}
+
+func TestFormatRelTimeNilReturnsDash(t *testing.T) {
+	var p *time.Time
+	if string(formatRelTime(p)) != "—" {
+		t.Errorf("nil should render as em-dash, got %q", formatRelTime(p))
+	}
+	if string(formatRelTime(time.Time{})) != "—" {
+		t.Errorf("zero should render as em-dash")
+	}
+}
+
+func TestRelTimeLabelBuckets(t *testing.T) {
+	cases := []struct {
+		d    time.Duration
+		want string
+	}{
+		{30 * time.Second, "30s ago"},
+		{5 * time.Minute, "5m ago"},
+		{2 * time.Hour, "2h ago"},
+		{3 * 24 * time.Hour, "3d ago"},
+		{2 * 7 * 24 * time.Hour, "2w ago"},
+		{-5 * time.Minute, "5m from now"},
+	}
+	for _, c := range cases {
+		if got := relTimeLabel(c.d); got != c.want {
+			t.Errorf("relTimeLabel(%v) = %q, want %q", c.d, got, c.want)
+		}
+	}
+}