mir-backend-jvm

Make It Right (JVM runtime tier). Java 25/21 LTS and Kotlin runtime reliability footguns shared across every JVM backend framework — distinct from the generic backend gates and from any one framework's mechanics. Covers: thread-pool sizing and pool-exhaustion deadlock, blocking I/O on platform threads, virtual threads after JEP 491 (synchronized no longer pins on Java 24+, jdk.VirtualThreadPinned JFR event) and…