🧪 Add tests for ScriptMutex::unlock

[Tcode-Motion]

🎯 What: The untested public function ScriptMutex::unlock inside stdlib/src/sync.rs is now tested.
📊 Coverage: A new threaded scenario test test_script_mutex_lock_unlock verifies that blocked threads on lock are properly awoken and can proceed when unlock is called.
✨ Result: Increased test coverage and confidence in thread synchronization logic for script mutices.

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PR created automatically by Jules for task 7968661651229805973 started by @Tcode-Motion

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