Add comments to Docker entrypoint explaining init container and sidecar modes

Author: DreierF

agent/src/docker/entrypoint.sh

@@ -1,7 +1,11 @@
 #!/bin/sh
+# When /transfer exists (shared volume), copy the agent JAR there and exit.
+# This supports the Kubernetes init container pattern where this image provides
+# the agent JAR to the application container via a shared volume.
 if [ -e /transfer ]; then
   cp -r /agent/teamscale-jacoco-agent.jar /transfer
   exit 0
 fi
+# Otherwise, keep the container alive indefinitely as a sidecar.
 trap : TERM INT
 sleep infinity & wait