Aerie and flying creatures: bats, chain gargoyles, arcane owls, ember wyrms

- New room: aerie (key Y, rooms category, campaign from mission 7); flyers sleep there
- Arrivals: aerie 4+ bats; + torture chamber gargoyles; + library owls; big aerie and treasury
  (16+ each) a rare ember wyrm; portal checks free places in lairs and aerie separately
- Flyers cross water and lava (path finding, flag, attacks), are not burnt by lava, patrol far
  when idle, attack single enemies, flee to the aerie below 25% health and rest there up to 75%
- Owls shoot arcane bolts, the wyrm breathes fire with splash damage; shots from the air
- Hovering sprites with flapping, aerie floor, perches, roosts, plinths, twig and ember nests
- Room counts are recounted on load (no longer stored); tests for flying and arrivals

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

src/settings.rs

@@ -7,7 +7,7 @@ use std::collections::BTreeMap;
 // Rebindable keyboard actions. Esc (menu) and the arrow keys (camera) are fixed.
 #[derive(Clone, Copy, PartialEq, Eq, Debug)]
 pub enum Action {
-    Tool(usize), // 0..18, same order as ui::TOOLS
+    Tool(usize), // 0..19, same order as ui::TOOLS
     CamForward,
     CamBack,
     CamLeft,
@@ -25,7 +25,7 @@ pub enum Action {
 }
 
 pub fn all_actions() -> Vec<Action> {
-    let mut v: Vec<Action> = (0..18).map(Action::Tool).collect();
+    let mut v: Vec<Action> = (0..19).map(Action::Tool).collect();
     v.extend_from_slice(&[
         Action::CamForward,
         Action::CamBack,
@@ -70,7 +70,7 @@ impl Action {
     fn default_key(self) -> KeyCode {
         use KeyCode::*;
         match self {
-            Action::Tool(i) => [Key1, Key2, Key3, Key4, Key5, Key6, Key7, Key8, Key9, Key0, X, V, K, J, B, C, T, U][i.min(17)],
+            Action::Tool(i) => [Key1, Key2, Key3, Key4, Key5, Key6, Key7, Key8, Key9, Key0, X, V, K, J, B, C, T, U, Y][i.min(18)],
             Action::CamForward => W,
             Action::CamBack => S,
             Action::CamLeft => A,