Integrate battles with the overworld UI and validate browser flows

- Drive wild battles through the real UI in Chromium and WebKit using a
  test-only encounter fixture: victory with level-up, escape, whiteout,
  mid-battle backup restore and unsupported-effect rollback.
- Add keyboard and on-screen D-pad navigation for battle menus.
- Accept pending stat experience in saves (awarded without CalcMonStats).
- Commit whiteout healing, money loss and destination callbacks together;
  aborted scripts restore state and map.
- Give long notices their own status-bar row on narrow screens.

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

src/game/runtime.ts

@@ -21,6 +21,8 @@ export class NativeRuntime implements GameRuntime {
     private onUpdate: (world: GameWorld) => void,
     private onError: (error: unknown) => void,
     private player: () => { name: string; avatar: "chris" | "kris" },
+    /** Presentation handles menu navigation; battle rules stay in the world. */
+    private battleInput?: (button: Button) => boolean,
   ) {}
   async load(bytes: Uint8Array, canvas: HTMLCanvasElement) {
     this.dispose();
@@ -55,9 +57,14 @@ export class NativeRuntime implements GameRuntime {
     if (this.pressed.has(button) || !this.world) return;
     this.pressed.add(button);
     const world = this.world;
+    if (world.battle && this.battleInput?.(button)) {
+      this.publish();
+      return;
+    }
     if (button === "a") world.interact();
     if (button === "b") world.advanceDialogue();
-    if ((button === "up" || button === "down") && world.dialogue?.choice)
+    if ((button === "up" || button === "down") &&
+        (world.dialogue?.choice || world.battle?.prompt?.kind === "yesno"))
       world.moveCursor(button);
     if ((button === "start" || button === "select") && !world.busy)
       world.notice =