fix: use daemon thread for version check to prevent JVM hang

[stalep]

Fixes #2523

Executors.newSingleThreadExecutor() creates non-daemon threads by default. After the version check task completes, the worker thread parks in LinkedBlockingQueue.take() waiting for tasks that never come, preventing JVM exit.

This causes jbang to occasionally hang indefinitely after a command completes.

Fix

Use a daemon thread factory with a descriptive thread name (jbang-version-check) so the JVM can exit normally when the main thread finishes.

Stack trace (from @maxandersen)

"pool-1-thread-1" #21 prio=5 cpu=216.66ms elapsed=112.83s
   java.lang.Thread.State: WAITING (parking)
    at java.util.concurrent.LinkedBlockingQueue.take(LinkedBlockingQueue.java:435)
    at java.util.concurrent.ThreadPoolExecutor.getTask(ThreadPoolExecutor.java:1070)
    at java.util.concurrent.ThreadPoolExecutor.runWorker(ThreadPoolExecutor.java:1130)
    ...

"DestroyJavaVM" #22 prio=5 cpu=185.54ms elapsed=112.67s
   java.lang.Thread.State: RUNNABLE

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[quintesse]

LGTM