Port the fishing rods and wild Magikarp

The Old, Good and Super Rods run FishFunction facing water: the map's fish
group and Fish pick no fish, no bite, or a Pokémon from FishGroups and the
time of day's TimeFishGroups. The player casts and jiggles with the
fishing frames drawn from LoadFishingGFX's tiles, shows "!" on a bite, and
the hooked Pokémon attacks as BATTLETYPE_FISH. Facing pieces now use
signed offsets, which the rod above and left of the player needs.

Wild Magikarp no longer stop a battle: LoadEnemyMon redraws their DVs
through CalcMagikarpLength and its filters, as the original does. The
length routine matches the original in the reference emulator.

Part of #27

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

src/game/rom/assets.ts

@@ -126,6 +126,7 @@ export class CrystalAssets {
       environment: r.byte(header + 2),
       paletteMode: r.byte(header + 7) & 15,
       phoneService: r.byte(header + 7) >> 4,
+      fishGroup: r.byte(header + 8),
       attributes,
       blocks: r.slice(r.far(attributes + 3), blockWidth * blockHeight),
       warps: [],
@@ -500,6 +501,24 @@ export class CrystalAssets {
       r.byte(entry + 2),
     );
   }
+  /** The first vTiles0 tile an emote's graphics are loaded to. */
+  emoteTile(index: number): number {
+    if (index < 0 || index > 11) throw new Error("Unknown emote.");
+    return (this.reader.word(SYMBOLS.emotes + index * 6 + 4) - 0x8000) >> 4;
+  }
+  /** LoadFishingGFX: the player's sprite (24 tiles) with the lower halves
+   * of the standing frames replaced by FishingGFX or KrisFishingGFX, then
+   * the two rod tiles that the fishing frames place at $fc and $fd. All
+   * of them are in VRAM bank 1, as the player's sprite is. */
+  fishingSprite(graphics: Uint8Array, kris: boolean): Uint8Array {
+    const source = kris ? OVERWORLD.KrisFishingGFX : OVERWORLD.FishingGFX;
+    const result = new Uint8Array(26 * 16);
+    result.set(graphics.subarray(0, 24 * 16));
+    [2, 6, 10, 24].forEach((tile, chunk) =>
+      result.set(this.reader.slice(source + chunk * 32, 32), tile * 16),
+    );
+    return result;
+  }
   /** HeadbuttTreeGFX: the shaking tree's two 2x2 frames, eight tiles. */
   headbuttTree(): Uint8Array {
     return this.reader.slice(OVERWORLD.HeadbuttTreeGFX, 8 * 16);
@@ -553,9 +572,11 @@ export class CrystalAssets {
       pointer = r.near(SYMBOLS.facings + facing * 2, r.bank(SYMBOLS.facings));
     return Array.from({ length: r.byte(pointer) }, (_, i) => {
       const p = pointer + 1 + i * 4;
+      // The offsets are added to the sprite's position modulo 256, so
+      // they act as signed bytes.
       return {
-        y: r.byte(p),
-        x: r.byte(p + 1),
+        y: (r.byte(p) << 24) >> 24,
+        x: (r.byte(p + 1) << 24) >> 24,
         attributes: r.byte(p + 2),
         tile: r.byte(p + 3),
       };

src/game/rom/profile.ts

@@ -161,6 +161,8 @@ export const RAM = {
   visitedSpawns: 0xdca5,
   tempWildMonSpecies: 0xd22e,
   coins: 0xd855,
+  /** hBGMapMode: HRAM, like hMoneyTemp below. */
+  bgMapMode: 0xffd4,
   blueCardBalance: 0xdc4b,
   /** hMoneyTemp: HRAM, not WRAM like the other entries above. */
   moneyTemp: 0xffc3,
@@ -274,6 +276,16 @@ export const OVERWORLD = {
   "_BasementKey.BasementKeyScript": 0x507e1,
   "_Squirtbottle.SquirtbottleScript": 0x5073c,
   "_Squirtbottle.CheckCanUseSquirtbottle": 0x50753,
+  FishGroups: 0x92488,
+  TimeFishGroups: 0x9266f,
+  Script_GotABite: 0xd035,
+  Script_NotEvenANibble: 0xd01e,
+  Script_NotEvenANibble2: 0xd027,
+  Fishing_CheckFacingUp: 0xd06c,
+  LoadFishingGFX: 0xb84b3,
+  PutTheRodAway: 0xd095,
+  FishingGFX: 0xb84f2,
+  KrisFishingGFX: 0xb8582,
   Flypoints: 0x91c5e,
   "TownMapBubble.Where": 0x91bf4,
   RuinsOfAlphKabutoChamber_MapAttributes: 0x958d0,
@@ -531,6 +543,9 @@ export const MENU = {
   CardKeyEffect: 0xf745,
   BasementKeyEffect: 0xf74c,
   SquirtbottleEffect: 0xf73e,
+  OldRodEffect: 0xf5a5,
+  GoodRodEffect: 0xf5a9,
+  SuperRodEffect: 0xf5ad,
   VitaminEffect: 0xee3d,
   RareCandyEffect: 0xef14,
   ItemStatRoseText: 0xeea6,
@@ -548,6 +563,8 @@ export const MENU = {
 /** Battle engine tables and texts, keyed by their PRET labels so that
  * \`npm run check:reference\` can verify each address by name. */
 export const BATTLE = {
+  HookedPokemonAttackedText: 0x8075c,
+  MagikarpLengths: 0xfbca8,
   ItemUsedText: 0xf83d,
   BallBrokeFreeText: 0xedb5,
   BallAppearedCaughtText: 0xedba,