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>

tests/battle.test.ts

@@ -179,7 +179,7 @@ describe.skipIf(!existsSync(romPath))(
     });
 
     it("refuses battles that need untranslated rules", () => {
-      const { battle: game } = battle([starter()], { species: 129, level: 5 });
+      const { battle: game } = battle([starter()], { species: 201, level: 5 });
       expect(() => play(game)).toThrow(UnsupportedBattle);
     });
   },