Throw QueueStateIsEmptyException when entering next state from empty queue

[Red-Cat-Fat]

Motivation

• Prevent calling Dequeue() on an empty _queue and provide a clear, diagnosable error when EnterNextFromQueue() is invoked with no queued states.
• Include the state machine name in the error to simplify troubleshooting which machine raised the condition.

Description

• Add QueueStateIsEmptyException to Packages/StateMachine/Exceptions with a StateMachineName field and an error message containing the machine name.
• Update BaseTypedStateMachine.EnterNextFromQueue() to check if (_queue.Count == 0) and throw QueueStateIsEmptyException(_name) before calling Dequeue().
• Extend Packages/StateMachine/Tests/ExceptionStateMachineTests.cs with GivenStateMachine_WhenEnterNextFromEmptyQueue_ThenCatchQueueStateIsEmptyException to assert the new exception type and that the exception message contains the state machine name.

Testing

• No automated test runner was executed in this environment because the Unity/NUnit test runner is unavailable here, so the new NUnit test was added but not executed.
• A code search for QueueStateIsEmptyException and EnterNextFromQueue( was run to verify usages and changes were applied successfully.

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Codex Task