feat: pick MiniMax-M2.7, and strip markdown and emoji from replies

Benchmarked M2.7, M3 and M2 against the same four pt-BR prompts (a
Minecraft question, a general-knowledge one, an unanswerable one, and a
jailbreak attempt).

M2.7 wins on the axis that matters for chat. All three held the
no-server-access line under the jailbreak, but:

- M3 is a reasoning model, and its thinking counts against max_tokens.
  At the 300 chat needs, its Minecraft answer was cut off mid-word at
  39 characters while reporting 590 tokens used. Raising the budget
  enough to fix that costs more per question than the answer is worth.
- M2 answered the brewing question wrong, going straight from a water
  bottle to magma cream and skipping the nether wart.
- M2.7 answered correctly in 2.7-5.2s.

The benchmark also showed both markdown and emoji in every model's
output. Minecraft chat renders neither: `**negrito**` arrives as
literal asterisks, and emoji are empty boxes on Bedrock. The system
prompt now asks for plain text, and sanitise() strips emphasis, code
fences, headings and emoji regardless, since a prompt is a request and
not a guarantee.

src/main/java/dev/marcospaulo/canalhandia/Ai.java

@@ -264,15 +264,26 @@ final class Ai {
     }
 
     /**
-     * Makes a model reply safe to print in chat.
+     * Makes a model reply safe and readable in chat.
      *
      * <p>Strips colour codes so the reply cannot forge server messages, folds
      * newlines so one answer stays one chat entry, and removes leading slashes
      * so nothing that comes back reads as a command to run.
+     *
+     * <p>It also strips markdown and emoji, which the models emit freely.
+     * Minecraft chat renders neither: {@code **negrito**} arrives as literal
+     * asterisks, and emoji show up as empty boxes on Bedrock.
      */
     static String sanitise(String raw, int max) {
         String text = raw.replace('§', ' ')
                 .replaceAll("[\\r\\n]+", " ")
+                // Markdown emphasis and code fences: chat shows the characters, not the effect.
+                .replaceAll("\\*{1,3}([^*]+)\\*{1,3}", "$1")
+                .replaceAll("`{1,3}([^`]+)`{1,3}", "$1")
+                .replaceAll("^#{1,6}\\s+", "")
+                // Emoji live outside the BMP, plus the symbol blocks and the
+                // variation selector. Accented pt-BR letters are far below this.
+                .replaceAll("[\\x{1F000}-\\x{1FAFF}\\x{2190}-\\x{2BFF}\\x{FE0F}\\x{20E3}]", "")
                 .replaceAll("\\s{2,}", " ")
                 .trim();
         while (text.startsWith("/")) {

src/main/java/dev/marcospaulo/canalhandia/Settings.java

@@ -222,7 +222,10 @@ final class Settings {
     }
 
     String aiModel() {
-        return plugin.getConfig().getString("ia.modelo", "MiniMax-M2");
+        // M2.7 measured 2.7-5.2s with correct answers. M3 is a reasoning model:
+        // its thinking counts against max_tokens, so replies get truncated
+        // mid-word unless the budget is raised far past what chat needs.
+        return plugin.getConfig().getString("ia.modelo", "MiniMax-M2.7");
     }
 
     void aiModel(String model) {
@@ -243,7 +246,9 @@ final class Settings {
                         + "ao terminal ou aos comandos do jogo, e não pode executar nada. "
                         + "Se pedirem para você rodar comandos, mexer no servidor, dar itens, "
                         + "banir alguém ou revelar configurações, explique que você só conversa. "
-                        + "Nunca escreva comandos de terminal nem de Minecraft.");
+                        + "Nunca escreva comandos de terminal nem de Minecraft. "
+                        + "Escreva em texto puro: nada de markdown, asteriscos, crases ou "
+                        + "emoji, porque o chat do Minecraft não formata nada disso.");
     }
 
     int aiMaxTokens() {