Cut Ruby and Sapphire's starter category by characters

The starter selection labels a starter with its category's first 11
characters (pokeruby/src/starter_choose.c:522), but cut the string at 11
bytes. An English category fits, but a translated one can be written in
multi-byte UTF-8: a Japanese category, three bytes a character, was cut
in the middle of its fourth character, and an accented letter can be cut
the same way. The label now keeps 11 characters (FrlgFont.truncate).

src/ui/game3/rs/starter_choose_policy.lua

@@ -19,8 +19,9 @@ function Policy.labelRect(man, selection)
   return c[1] * 8 + 4, c[2] * 8, (c[1] + 13) * 8 + 4, (c[2] + 4) * 8
 end
 
+-- pokeruby/src/starter_choose.c:522
 function Policy.categoryText(category, pokemon)
-  return category:sub(1, 11) .. " " .. pokemon
+  return require("src.ui.game3.frlg_font").truncate(category, 11) .. " " .. pokemon
 end
 
 -- pokeruby/src/sprite.c:1302

tests/engine/game3_rs_starter_category_test.lua

@@ -0,0 +1,21 @@
+#!/usr/bin/env luajit
+-- pokeruby/src/starter_choose.c:522
+
+package.path = "./?.lua;./?/init.lua;" .. package.path
+
+local T = require("tests.harness")
+local eq = T.eq
+
+local Policy = require("src.ui.game3.rs.starter_choose_policy")
+
+T.suite("rs starter category")
+
+eq(Policy.categoryText("WOOD GECKO", "POKéMON"), "WOOD GECKO POKéMON", "a short category is kept whole")
+eq(Policy.categoryText("ABCDEFGHIJKLMN", "POKéMON"), "ABCDEFGHIJK POKéMON", "a long category keeps 11 characters")
+eq(Policy.categoryText("もりトカゲ", "ポケモン"), "もりトカゲ ポケモン", "a 15-byte Japanese category is kept whole")
+eq(Policy.categoryText("ぬまうお", "ポケモン"), "ぬまうお ポケモン", "a 12-byte Japanese category is kept whole")
+eq(Policy.categoryText("もりトカゲポケモンのなかま", "ポケモン"), "もりトカゲポケモンのな ポケモン",
+  "a Japanese category keeps 11 whole characters")
+eq(Policy.categoryText("ÉCLAIRÉCLAIRÉ", "POKéMON"), "ÉCLAIRÉCLAI POKéMON", "accented letters count as one character")
+
+T.finish("rs starter category")