feat(battle-engine): close the AI-simulation subsystem (verbatim)

Copied the 89 uncopied AI*SimulationUtility/extension files defining the
AIVirtualCard/AIVirtualField extension methods; the compile loop then auto-closed
the revealed type deps (~3049 files total, drift-clean). 10.0k -> 62 errors.

SVSim.BattleEngine/Engine/Cute/LeanThreadPool.cs

@@ -0,0 +1,106 @@
+using System;
+using System.Collections;
+using System.Collections.Generic;
+using System.Threading;
+using UnityEngine;
+
+namespace Cute;
+
+public class LeanThreadPool
+{
+	private static LeanThreadPool _instance;
+
+	private Thread[] _threads;
+
+	private Semaphore _semaphore;
+
+	private object _jobsLock;
+
+	private object _convergeLock;
+
+	private List<ParallelJob> _jobs;
+
+	private bool _quit;
+
+	private int _convergeCount;
+
+	public static LeanThreadPool Instance
+	{
+		get
+		{
+			if (_instance == null)
+			{
+				_instance = new LeanThreadPool();
+			}
+			return _instance;
+		}
+	}
+
+	public int ThreadsCount => _threads.Length;
+
+	private LeanThreadPool()
+	{
+		int processorCount = SystemInfo.processorCount;
+		_jobs = new List<ParallelJob>();
+		_jobsLock = new object();
+		_convergeLock = new object();
+		_semaphore = new Semaphore(0, int.MaxValue);
+		_threads = new Thread[processorCount];
+		for (int i = 0; i < _threads.Length; i++)
+		{
+			_threads[i] = new Thread(ThreadFunction);
+			_threads[i].Start();
+		}
+	}
+
+	private void ThreadFunction()
+	{
+		ParallelJob parallelJob = null;
+		while (!_quit)
+		{
+			_semaphore.WaitOne();
+			lock (_jobsLock)
+			{
+				if (_jobs.Count > 0)
+				{
+					parallelJob = _jobs[0];
+					_jobs.Remove(parallelJob);
+				}
+			}
+			if (parallelJob != null)
+			{
+				parallelJob.Run();
+				parallelJob = null;
+			}
+		}
+		lock (_convergeLock)
+		{
+			_convergeCount++;
+		}
+	}
+
+	public IEnumerator KillAll(Action callback = null)
+	{
+		_quit = true;
+		_convergeCount = 0;
+		lock (_jobsLock)
+		{
+			_jobs.Clear();
+		}
+		_semaphore.Release(_threads.Length);
+		while (_convergeCount < _threads.Length)
+		{
+			yield return 0;
+		}
+		callback.Call();
+	}
+
+	public void AddJob(ParallelJob job)
+	{
+		lock (_jobsLock)
+		{
+			_jobs.Add(job);
+		}
+		_semaphore.Release();
+	}
+}