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>

tests/battle-fixture.ts

@@ -0,0 +1,37 @@
+import { CrystalAssets } from "../src/game/rom/assets";
+import { generatePartyMon } from "../src/game/party/pokemon";
+import { GameWorld } from "../src/game/world/world";
+
+export type BattleScenario = "win" | "loss" | "unsupported";
+
+/** Test-only encounters on an existing floor: production maps stay gated.
+ * Everything after selection runs through the ROM's real wild-battle script. */
+export function battleFixtureWorld(assets: CrystalAssets, scenario: BattleScenario = "win") {
+  assets.grassCollisions = () => [assets.collision(assets.map("24:7"), 3, 2)];
+  assets.grassWildMons = (id) => id === "24:7" ? {
+    rates: [256, 256, 256],
+    slots: [0, 1, 2].map(() => Array.from({ length: 7 }, () => ({ species: 16, level: 3 }))),
+  } : undefined;
+  let seed = 1;
+  const world = new GameWorld(assets, () => new Date("2026-09-22T12:00:00"), () => {
+    seed = (seed * 1103515245 + 12345) >>> 0;
+    return (seed >>> 16) & 255;
+  });
+  const mon = generatePartyMon(assets.pokemon, {
+    species: 155, level: 5, item: 0, otId: world.playerId,
+    ot: "CHRIS", dvs: 0x823b, caughtData: 0,
+  });
+  mon.exp = 178; // One battle away from level 6 and Smokescreen.
+  if (scenario === "loss") mon.hp = 1;
+  if (scenario === "unsupported") {
+    mon.moves = [144, 0, 0, 0]; // Transform is explicitly refused.
+    mon.pp = [10, 0, 0, 0];
+  }
+  world.state.party.push(mon);
+  world.state.pokedex.seen.add(155);
+  world.state.pokedex.caught.add(155);
+  world.state.money = 3001;
+  return world;
+}
+
+export const ENCOUNTER_WALK = ["up", "right", "right", "right", "right"] as const;