Handle Velocity reconfiguration chat session updates

[minekube-ai]

Summary

• allow the Velocity Connect tunnel chat-session filter to resolve/drop the chat-session update packet while Velocity is in CONFIGURATION, not only PLAY
• add a regression test for the Reconfiguring path using the existing embedded Netty/Velocity decoder harness

Red reproduction

• JAVA_HOME=/tmp/codex-jdk PATH=/tmp/codex-jdk/bin:$PATH ./gradlew :velocity:test --tests com.minekube.connect.inject.velocity.VelocityChatSessionPacketFilterTest.derivesChatSessionUpdatePacketIdWhileVelocityReconfiguresBackendConnection
• Result before implementation: failed at VelocityChatSessionPacketFilterTest.java:149 because the PLAY-only guard passed the packet through instead of dropping it.

Green verification

• JAVA_HOME=/tmp/codex-jdk PATH=/tmp/codex-jdk/bin:$PATH ./gradlew :velocity:test --tests com.minekube.connect.inject.velocity.VelocityChatSessionPacketFilterTest
• Result after implementation: BUILD SUCCESSFUL in 7s, 27 actionable tasks, 7 executed.

Proof gap

• I did not run a real Minecraft client / MIN-24 harness check in this environment. This PR is verified with the existing focused packet-filter unit harness, which proves the CONFIGURATION-state packet handling but not full Gate + Velocity + Purpur 26.2 end-to-end behavior.