refactor: extract AiText and detect foreign-script leakage

Moves sanitise out of the Bukkit-bound Ai class so it can be unit
tested, and adds hasForeignScript to catch the CJK words the model
intermittently drops into Portuguese answers.

Colour-code stripping now removes the code character too: replacing
only the section sign left "§c" reading as a stray "c" in chat.

Surefire now fails on an empty suite, so a misplaced or disabled test
class cannot pass as a green build.

Co-Authored-By: Claude Opus 5 <noreply@anthropic.com>
Claude-Session: https://claude.ai/code/session_01F3jSvSTrG4qsniLSr6TpC6

pom.xml

@@ -68,6 +68,13 @@
         <groupId>org.apache.maven.plugins</groupId>
         <artifactId>maven-surefire-plugin</artifactId>
         <version>3.5.4</version>
+        <configuration>
+          <!-- The pin above guards against a surefire version that quietly stops
+               discovering tests. It does not guard against a test class being
+               misplaced, misnamed or disabled, which ends the same way: a green
+               build that ran nothing. Failing on an empty suite closes that gap. -->
+          <failIfNoTests>true</failIfNoTests>
+        </configuration>
       </plugin>
     </plugins>
   </build>