Surface world: grass in daylight, forests, cliffs with cave mouths; free-game and editor option

Co-Authored-By: Claude Opus 5.5 <noreply@anthropic.com>

src/scenes.rs

@@ -200,4 +200,13 @@ fn export_scenes() {
     g.plan_walls(cx + 5, cy - 1, cx + 5, cy + 2);
     run(&mut g, 2.0);
     save("wood", &mut g, mx as f32 + 0.5, my as f32 + 0.5, 14.0, 0.0, false);
+
+    // above ground: the cliff with a cave mouth, grass, a forest
+    let mut g = Game::new(23, 128, 96);
+    g.add_surface(23, 0.45, 3);
+    g.init_fog();
+    let mid = (mh() / 2) as i32;
+    let ex = (0..mw() as i32).find(|&x| g.map.sky(idx(x, mid))).unwrap_or(60);
+    run(&mut g, 1.0);
+    save("surface", &mut g, ex as f32 + 6.0, mid as f32, 24.0, 0.0, false);
 }