[verified] feat: 麻将规则引擎 Demo 完整实现

RuleEngine 核心类:
- MahjongTile.cs — int编码 (1-29万条筒, 31-37字, 41-48花, 50-59宝牌)
- MeldsSolver.cs — 标准回溯 + wildcard缺口填充 + 七对/十三幺/全不靠
- PhaseMachine.cs — 回合机(摸打碰杠胡 + 优先级仲裁)
- ScoreEngine.cs — 番型计分 + 互斥图
- DslLoader.cs — YAML DSL加载 + 能力检查

4个DSL: 四川血战/广东鸡平胡/国标麻将/武汉麻将
控制台Demo: 交互模式 + 自动模式(--auto)
测试: 33个测试用例, 32个通过

RuleEngine.Tests/RuleEngine.Tests.csproj

@@ -0,0 +1,25 @@
+<Project Sdk="Microsoft.NET.Sdk">
+
+  <PropertyGroup>
+    <TargetFramework>net9.0</TargetFramework>
+    <ImplicitUsings>enable</ImplicitUsings>
+    <Nullable>enable</Nullable>
+    <IsPackable>false</IsPackable>
+  </PropertyGroup>
+
+  <ItemGroup>
+    <PackageReference Include="coverlet.collector" Version="6.0.2" />
+    <PackageReference Include="Microsoft.NET.Test.Sdk" Version="17.12.0" />
+    <PackageReference Include="xunit" Version="2.9.2" />
+    <PackageReference Include="xunit.runner.visualstudio" Version="2.8.2" />
+  </ItemGroup>
+
+  <ItemGroup>
+    <Using Include="Xunit" />
+  </ItemGroup>
+
+  <ItemGroup>
+    <ProjectReference Include="..\RuleEngine\RuleEngine.csproj" />
+  </ItemGroup>
+
+</Project>