Updated Iris packaging

- Version is 4.1.2-26.2 across platform builds
- Plugin builds use shared automatic jar selection
- Native adapters remain bundled in selected artifacts
- Plugin export tasks copy the selected artifact
- The previous plugin packer is removed
- The agent tracks primary storage closure during Spigot shutdown

gradle.properties

@@ -21,7 +21,7 @@ org.gradle.jvmargs=-Xmx3072m -XX:+HeapDumpOnOutOfMemoryError -Dfile.encoding=UTF
 org.gradle.caching=true
 org.gradle.configureondemand=false
 
-irisVersion=4.1.1-26.2
+irisVersion=4.1.2-26.2
 minecraftVersion=26.2
 # Bukkit plugin api-version: lowest supported Minecraft release line so one artifact loads on 26.1.2 and 26.2
 apiVersion=26.1