Initial Fabric mod for chat-based quiz answer submission

Hooks ServerMessageEvents.ALLOW_CHAT_MESSAGE to intercept chat while the
music_quiz datapack is in answer-accepting state (init=5 on objective
'main'). Intercepted messages are forwarded to mq:answer/submit with the
player's UUID context and the chat broadcast is suppressed so the answer
stays hidden from other players. Outside that state chat passes through
normally.

Target: Minecraft 1.21.6+, Java 21, Fabric Loader 0.16+, Fabric API.

Co-Authored-By: Claude Opus 4.7 <noreply@anthropic.com>

settings.gradle

@@ -0,0 +1,9 @@
+pluginManagement {
+    repositories {
+        maven { url = 'https://maven.fabricmc.net/' }
+        gradlePluginPortal()
+        mavenCentral()
+    }
+}
+
+rootProject.name = 'chat_answer'