Port the special battle types and contest battles

Run the forced-shiny, trap, forced-item, Celebi, Suicune, roaming and Bug-Catching Contest battle types. Roaming battles keep their struct's DVs and HP byte, and every other battle makes CleanUpBattleRAM's roaming roll. The contest shows PARKBALL×, counts down Park Balls, ends when they run out, keeps its catch outside the party and asks before switching. Scripts load the special types with loadvar, and while a contest runs, encounters use BugCatchingContestBattleScript and ContestMons.

Validated with 596 unit tests, 155 browser tests (including the contest menu and switch screen), native/reference builds and reference/vendor/release checks. National Park's contest event, the roaming release and the Ilex Forest Celebi event come with their maps.

Closes #28

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

src/game/world/world.ts

@@ -348,7 +348,17 @@ export interface BattleView {
   /** A choice the battle is waiting for, if any. */
   prompt?: Extract<
     BattleEffect,
-    { kind: "action" | "yesno" | "forget" | "stats" | "name" | "party" | "move" }
+    {
+      kind:
+        | "action"
+        | "yesno"
+        | "contestswitch"
+        | "forget"
+        | "stats"
+        | "name"
+        | "party"
+        | "move";
+    }
   >;
   /** Yes/No cursor, as on the original boxes. */
   selected: 0 | 1;
@@ -1565,6 +1575,7 @@ export class GameWorld {
     )
       return;
     if (isIce(collision)) return;
+    if (state.bugContest) return this.bugContestEncounter(previous, collision);
     const table = this.encounterTable(state);
     if (!(this.random() < table.rate)) return;
     const chosen = this.chooseWildEncounter(table);
@@ -1581,6 +1592,40 @@ export class GameWorld {
     // The step replays after a reload, so it keeps its Repel step.
     if (state.repel && this.script) this.script.committed.repel++;
   }
+  /** _TryWildEncounter_BugContest: 40% in super tall grass and 20%
+   * elsewhere (halved by a Cleanse Tag; no radio music changes it yet),
+   * a ContestMons pick, the Repel check, then
+   * BugCatchingContestBattleScript. */
+  private bugContestEncounter(previous: { x: number; y: number }, collision: number) {
+    const state = this.state;
+    let rate = Math.floor(
+      ((collision === OW.COLL_LONG_GRASS || collision === OW.COLL_LONG_GRASS_1C ? 40 : 20) * 255) / 100,
+    );
+    if (state.party.some((mon) => mon.item === C.CLEANSE_TAG)) rate >>= 1;
+    if (!(this.random() < rate)) return;
+    // ChooseWildEncounter_BugContest: 0-99, then percentages in ContestMons.
+    let roll: number;
+    do roll = this.random();
+    while (roll >= 200);
+    roll >>= 1;
+    const r = this.assets.reader;
+    let entry = OVERWORLD.ContestMons;
+    while (roll >= r.byte(entry)) {
+      roll -= r.byte(entry);
+      entry += 4;
+    }
+    const species = r.byte(entry + 1),
+      min = r.byte(entry + 2),
+      span = r.byte(entry + 3) - min;
+    const level = span ? min + (this.random() % (span + 1)) : min;
+    const lead = state.party.find((mon) => mon.hp > 0);
+    if (!lead || (state.repel && level < lead.level)) return;
+    this.startScript(OVERWORLD.BugCatchingContestBattleScript, PLAYER, {
+      committedPosition: previous,
+      wild: { species, level },
+    });
+    if (state.repel && this.script) this.script.committed.repel++;
+  }
   /** GetMapEncounterRate: CheckOnWater picks the water table and rate,
    * which a Cleanse Tag halves. */
   private encounterTable(state: ScriptState) {
@@ -2456,6 +2501,8 @@ export class GameWorld {
           canLose: effect.canLose,
           tree: effect.tree,
           fish: effect.fish,
+          battleType: effect.battleType,
+          contest: draft.bugContest,
           mapId: this.mapId,
           text: () => this.host(PLAYER).text(),
           bag: draft.bag,
@@ -3172,6 +3219,7 @@ export class GameWorld {
     const prompt = this.battle?.prompt;
     if (
       prompt?.kind === "yesno" ||
+      prompt?.kind === "contestswitch" ||
       prompt?.kind === "forget" ||
       prompt?.kind === "party" ||
       prompt?.kind === "move"
@@ -3182,7 +3230,8 @@ export class GameWorld {
   private battleA() {
     const view = this.battle!;
     const prompt = view.prompt;
-    if (prompt?.kind === "yesno") return this.pumpBattle(view.selected);
+    if (prompt?.kind === "yesno" || prompt?.kind === "contestswitch")
+      return this.pumpBattle(view.selected);
     if (prompt?.kind === "stats") return this.pumpBattle();
     if (!prompt && view.message?.prompt) this.pumpBattle();
   }
@@ -3190,7 +3239,8 @@ export class GameWorld {
   private battleB() {
     const view = this.battle!;
     const prompt = view.prompt;
-    if (prompt?.kind === "yesno") return this.pumpBattle(0);
+    if (prompt?.kind === "yesno" || prompt?.kind === "contestswitch")
+      return this.pumpBattle(0);
     if (prompt?.kind === "forget") return this.pumpBattle(4);
     if (prompt?.kind === "party" && prompt.cancel) return this.pumpBattle(-1);
     if (prompt?.kind === "move") return this.pumpBattle(-1);
@@ -4046,7 +4096,8 @@ export class GameWorld {
   }
   /** Change the highlighted answer (up/down on the original menus). */
   moveCursor(direction: Direction) {
-    if (this.battle?.prompt?.kind === "yesno") {
+    const battlePrompt = this.battle?.prompt?.kind;
+    if (this.battle && (battlePrompt === "yesno" || battlePrompt === "contestswitch")) {
       if (direction === "up") this.battle.selected = 1;
       if (direction === "down") this.battle.selected = 0;
       return;