feat: add local NuGet development workflow

Add a local NuGet feed configuration, a Directory.Build.props
template for Godot users, and automate source generator bundling
into the NuGet package.

.gitignore

@@ -15,6 +15,7 @@ x86/
 !**/[Pp]ackages/build/
 *.nuget.props
 *.nuget.targets
+nupkgs/
 
 # IDE
 .vs/

Directory.Build.props.godot-template

@@ -0,0 +1,21 @@
+<!--
+  Directory.Build.props for Godot C# projects consuming OECS.
+  Godot regenerates .csproj files on certain editor actions, which can
+  wipe custom <ItemGroup> entries. This file is never touched by Godot.
+
+  Placement: put this file in the root of your Godot project (next to
+  the .sln file), or in any parent directory.
+
+  You also need a nuget.config next to your .sln with the local feed:
+  <?xml version="1.0" encoding="utf-8"?>
+  <configuration>
+    <packageSources>
+      <add key="local-oecs" value="path/to/oecs-sharp/nupkgs" />
+    </packageSources>
+  </configuration>
+-->
+<Project>
+  <ItemGroup>
+    <PackageReference Include="OECS" Version="0.1.*" />
+  </ItemGroup>
+</Project>

nuget.config

@@ -0,0 +1,9 @@
+<?xml version="1.0" encoding="utf-8"?>
+<configuration>
+  <packageSources>
+    <!-- Local feed for OECS development builds.
+         Run `dotnet pack src/OECS/OECS.csproj -c Release -o ./nupkgs`
+         to produce the package. -->
+    <add key="local-oecs" value="./nupkgs" />
+  </packageSources>
+</configuration>

src/OECS/OECS.csproj

@@ -23,4 +23,20 @@
     <PackageReference Include="R3" Version="1.2.9" />
   </ItemGroup>
 
+  <!-- Bundle the source generator into the NuGet package as an analyzer.
+       Consumers get compile-time component discovery automatically. -->
+  <ItemGroup>
+    <None Include="..\OECS.SourceGen\bin\$(Configuration)\netstandard2.0\OECS.SourceGen.dll"
+          Pack="true" PackagePath="analyzers/dotnet/cs" Visible="false" />
+  </ItemGroup>
+
+  <!-- Ensure the source generator is built before packing.
+       Skipped when NoBuild property is set to true. -->
+  <Target Name="BuildSourceGenerator" BeforeTargets="GenerateNuspec"
+          Condition="'$(NoBuild)' != 'true'">
+    <MSBuild Projects="..\OECS.SourceGen\OECS.SourceGen.csproj"
+             Targets="Build"
+             Properties="Configuration=$(Configuration)" />
+  </Target>
+
 </Project>