Add scripted trainer battle foundation and native move AI

src/game/scripts/text.ts

@@ -71,6 +71,7 @@ const CHARACTERS: Record<number, string> = {
 export interface TextContext {
   player: string;
   rival: string;
+  trainer?: string;
   mom: string;
   /** Native strings stored at the RAM addresses named by text_ram. */
   strings: Readonly<Record<number, string>>;
@@ -126,6 +127,7 @@ function character(code: number, context: TextContext): string | undefined {
   if (code === 0x5a) return battler(context, context.battle?.turn === 1);
   if (code === 0x52 || code === 0x14) return context.player;
   if (code === 0x53) return context.rival;
+  if (code === 0x3f) return context.trainer;
   if (code === 0x49) return context.mom;
   if (code >= 0x80 && code <= 0x99)
     return String.fromCharCode(65 + code - 0x80);