A fix is ready and verified on current Debian (default-jdk OpenJDK 26): replace the deprecated-for-removal Thread.stop() in LessonRunner.stopAll() with cooperative Thread.interrupt(), so PLM's in-process recompilation of its framework sources no longer fails and Java exercises run again.
Forwarded upstream: https://github.com/BuggleInc/PLM/pull/528 This is independent of the (separate, gated) Scala 2.12 migration, so I plan to upload it as a standalone NMU together with the fix for #1139932, rather than hold it behind the Scala work.
