🧪 Add concurrent test for ScriptMutex::unlock

[Tcode-Motion]

🎯 What: Added a concurrent test for the previously untested public function ScriptMutex::unlock in stdlib/src/sync.rs.

📊 Coverage: Covered the thread synchronization scenario, ensuring that calling unlock from one thread correctly notifies other threads blocked on lock.

✨ Result: Increased test coverage by validating the inter-thread wakeup mechanism of ScriptMutex.

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PR created automatically by Jules for task 1439372915663548326 started by @Tcode-Motion

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