Long expeditions D1-a: graph-driven TotalRooms; goblin_warrens 7→16

Length is now sourced from the zone graph's longest entry→boss path,
not the dice roll, so "Room X/Y" matches what the player walks. The
dice fallback stays for graphless zones.

Goblin Warrens grows to the T1 12–14 band (13-node traversal): adds the
missing Trap anchor and deepens both fork branches + the post-merge
approach. Pattern reference for the remaining zones in D1-b…d.

internal/plugin/dnd_zone_test.go

@@ -126,9 +126,12 @@ func TestZoneRegistry_LootDropChances(t *testing.T) {
 }
 
 func TestZoneRegistry_RoomCountSane(t *testing.T) {
+	// Long-expedition plan §2 widens the bands per tier: T1 12–14 up to
+	// T5 ~36–44. The guard floor stays at 5 (no zone should ever drop
+	// below that) and the ceiling tracks the T5 target.
 	for _, z := range allZones() {
-		if z.MinRooms < 5 || z.MaxRooms > 10 || z.MinRooms > z.MaxRooms {
-			t.Errorf("zone %s rooms %d-%d outside design (5-10, min<=max)",
+		if z.MinRooms < 5 || z.MaxRooms > 44 || z.MinRooms > z.MaxRooms {
+			t.Errorf("zone %s rooms %d-%d outside design (5-44, min<=max)",
 				z.ID, z.MinRooms, z.MaxRooms)
 		}
 	}