Adventure news: add zone_clear event type

gogobee now splits the realm's first-ever clear (zone_first, priority)
from a later repeat (zone_clear, bulletin) so a repeat is never filed as
a first-ever. Handle both:

- renderAdventure: zone_first keeps the "cleared for the very first
  time" headline; zone_clear gets the personal "{subject} clears {zone}"
  headline, sharing the lede. A tier fallback still handles a legacy
  zone_first that predates the split.
- advEventMeta: zone_clear -> "Zone cleared" (distinct from zone_first's
  "First clear"), so a repeat's permalink page and emblem aren't stamped
  "First clear".

The GUID contract is otherwise unchanged: prefix == event_type, so the
permalink label derives correctly. Test: TestRenderZoneTaxonomy.

Deploy this before the matching gogobee change — a zone_clear fact hits
an un-updated Pete as an unknown event_type (400).

internal/web/adventure_test.go

@@ -194,6 +194,30 @@ func TestAdventureDigest(t *testing.T) {
 // TestAdventureArtAndMeta covers the visual-identity slice: the emblem endpoint
 // returns a themed SVG, ingested cards carry its local path, and the permalink
 // page is noindex with an og:image.
+// TestRenderZoneTaxonomy: a realm-first (zone_first) reads as first-ever; a
+// repeat (zone_clear) reads as a personal clear, not a mis-labeled "first".
+func TestRenderZoneTaxonomy(t *testing.T) {
+	first := AdvFact{EventType: "zone_first", Tier: "priority", Subject: "Brannigan",
+		Zone: "Dragon's Lair", Region: "the Underforge", Level: 14}
+	hl, _, ok := renderAdventure(first)
+	if !ok || !strings.Contains(hl, "very first time") {
+		t.Errorf("zone_first headline = %q (ok=%v)", hl, ok)
+	}
+
+	repeat := AdvFact{EventType: "zone_clear", Tier: "bulletin", Subject: "Brannigan",
+		Zone: "Dragon's Lair", Region: "the Underforge", Level: 14}
+	hl2, _, ok := renderAdventure(repeat)
+	if !ok || !strings.Contains(hl2, "Brannigan clears") || strings.Contains(hl2, "first") {
+		t.Errorf("zone_clear headline = %q (ok=%v)", hl2, ok)
+	}
+
+	// The permalink label distinguishes the two, so a repeat's page isn't stamped
+	// "First clear".
+	if lbl, _ := advEventMeta("zone_clear"); lbl == "First clear" {
+		t.Errorf("zone_clear meta label = %q, want distinct from first clear", lbl)
+	}
+}
+
 func TestAdventureArtAndMeta(t *testing.T) {
 	const token = "t"
 	s, _ := newAdvServer(t, token)