feat: 新增方案 C 的 Handoff 路由宿主，并让抽城市支持自然语言。

把图 JSON 编译成 CreateHandoffBuilderWith + WithHandoff；Agent 固定 Id 以免交接工具名错位；DeepSeek 关闭 thinking，避免多轮丢掉 reasoning_content 导致 400。

MAF1.Core/MAF1.Core.csproj

@@ -10,9 +10,11 @@
 
   <ItemGroup>
     <Compile Include="Agents\AgentStepResult.cs" />
+    <Compile Include="Agents\SystemNodeTypes.cs" />
     <Compile Include="Agents\FileCity\CityExtraction.cs" />
     <Compile Include="Agents\FileCity\FileCityAgent.cs" />
     <Compile Include="Agents\Weather\WeatherAgent.cs" />
+    <Compile Include="Decisions\ConsoleDecisionPrompt.cs" />
     <Compile Include="Decisions\DecisionModels.cs" />
     <Compile Include="PluginContract\PluginManifest.cs" />
     <Compile Include="PluginContract\PluginStdio.cs" />
@@ -20,6 +22,7 @@
     <Compile Include="Tools\WeatherOptions.cs" />
     <Compile Include="Tools\WeatherTools.cs" />
     <Compile Include="Utils\AgentFactory.cs" />
+    <Compile Include="Utils\DeepSeekThinking.cs" />
     <Compile Include="Utils\JsonText.cs" />
     <Compile Include="Utils\LlmOptions.cs" />
     <Compile Include="Utils\WindowsConsole.cs" />