chore(build): 配置项目构建属性以支持源代码生成器

- 为 GFramework.Godot 项目添加 GodotProjectDir 属性默认值
- 在 GFramework 元包中添加 NoPackageAnalysis 属性配置
- 为不同 .NET 版本添加占位符文件到包输出中
- 确保源代码生成器在标准 SDK 构建中正常运行

GFramework.Godot/GFramework.Godot.csproj

@@ -6,6 +6,9 @@
         <Nullable>enable</Nullable>
         <TargetFrameworks>net8.0;net9.0;net10.0</TargetFrameworks>
         <GenerateDocumentationFile>true</GenerateDocumentationFile>
+        <!-- Godot.SourceGenerators expects this property from Godot.NET.Sdk.
+             Provide a safe default so source generators can run in plain SDK-style builds as well. -->
+        <GodotProjectDir Condition="'$(GodotProjectDir)' == ''">$(MSBuildProjectDirectory)</GodotProjectDir>
     </PropertyGroup>
 
     <ItemGroup>

GFramework.csproj

@@ -16,11 +16,16 @@
         <PackageReadmeFile>README.md</PackageReadmeFile>
         <TargetFrameworks>net8.0;net9.0;net10.0</TargetFrameworks>
         <IncludeBuildOutput>false</IncludeBuildOutput>
+        <!-- This package is a pure meta-package that only aggregates dependencies. -->
+        <NoPackageAnalysis>false</NoPackageAnalysis>
     </PropertyGroup>
 
     <!-- 排除不需要参与打包/编译的目录 -->
     <ItemGroup>
         <None Include="README.md" Pack="true" PackagePath=""/>
+        <None Include="packaging/_._" Pack="true" PackagePath="lib/net8.0/_._"/>
+        <None Include="packaging/_._" Pack="true" PackagePath="lib/net9.0/_._"/>
+        <None Include="packaging/_._" Pack="true" PackagePath="lib/net10.0/_._"/>
         <None Remove="GFramework.Core\**"/>
         <None Remove="GFramework.Game\**"/>
         <None Remove="GFramework.Godot\**"/>

packaging/_._

@@ -0,0 +1 @@
+