m2e resolves the local repository from the Maven settings XML, never from
-Dmaven.repo.local, so JDTLS imports kept downloading into ~/.m2/repository
even when the IDE's own mvn runs honored the configured path. When a local
repository is configured but the user settings lack <localRepository>, derive
an effective settings file under <root>/.openidea/ and pass it as
java.configuration.maven.userSettings. Settings that already declare
<localRepository> are passed through untouched.