Long expeditions D1-b: crypt_valdris + T2 zones to new room bands

Three more zones follow the goblin_warrens pattern from D1-a: add the
missing Trap anchor and deepen the graph so the longest entry→boss walk
lands in its tier's target band.

  crypt_valdris  (T1):  8 → 17 nodes, longest 13 (band 12–14)
  forest_shadows (T2):  9 → 19 nodes, longest 16 (band 16–20)
  sunken_temple  (T2): 10 → 26 nodes, longest 16 (band 16–20)

Topology preserved per zone:
- Crypt diamond + Perception-DC-15 secret off side_chapel.
- Forest asymmetric main fork (long branch carries the elite) +
  WIS-DC-14 secret pre-boss.
- Sunken Temple sequential forks with no mid-path merge (four leaves
  all terminate at the single boss room).

MinRooms/MaxRooms re-pitched to the §2 bands so the dice fallback also
lands in band for any future graphless zone.

internal/plugin/zone_graph_sunken_temple_test.go

@@ -13,8 +13,12 @@ func TestSunkenTempleGraph_Registered(t *testing.T) {
 	if g.Boss != "sunken_temple.boss" {
 		t.Errorf("boss node = %q", g.Boss)
 	}
-	if len(g.Nodes) != 10 {
-		t.Errorf("nodes = %d, want 10", len(g.Nodes))
+	// Long-expedition D1-b widened this zone from 10 → 26 nodes so the
+	// longest entry→boss walk lands in the T2 [16,20] traversal band.
+	// (Sunken Temple is wide by design — no mid-merge means each leaf
+	// owns its own chain to the boss.)
+	if len(g.Nodes) != 26 {
+		t.Errorf("nodes = %d, want 26", len(g.Nodes))
 	}
 }