fix: reference all Unity managed DLLs via MSBuild glob

DocFX v2 requires Roslyn to resolve Unity types (MonoBehaviour, AudioClip,
etc.) to their fully-qualified UIDs before the xref map can link them to
docs.unity3d.com. Without assembly references, crefs become !:AudioClip
which never matches the xref map.

A MSBuild Target globs all *.dll from $(UnityManagedPath) (defaulting to
lib/UnityEngine/, populated by CI) so users never need to manually add
<Reference> entries when new Unity types are used in their scripts.

UNITY_MANAGED_PATH env var allows pointing to a local Unity installation
for development without running Docker.

.gitignore: replace broad *.csproj + negation with specific Unity-generated
patterns (Assembly-CSharp*.csproj) so DocFxForUnity.csproj stays tracked
without a fragile negation rule. Add lib/ to ignore extracted DLLs.

https://claude.ai/code/session_01N4YoJdJc2JDaoAbk5Nt8vf

Author: claude

.gitignore

@@ -30,8 +30,9 @@ Packages/*
 ## Autogenerated VS/MD/Consulo solution and project files
 ExportedObj/
 .consulo/
-*.csproj
-!DocFxForUnity.csproj
+Assembly-CSharp*.csproj
+Assembly-CSharp-Editor*.csproj
+lib/
 *.unityproj
 *.sln
 *.suo

DocFxForUnity.csproj

@@ -1,5 +1,24 @@
 <Project Sdk="Microsoft.NET.Sdk">
   <PropertyGroup>
     <TargetFramework>netstandard2.1</TargetFramework>
+    <!--
+      In CI: Unity managed DLLs are extracted to lib/UnityEngine/ by the workflow.
+      Locally: set the UNITY_MANAGED_PATH environment variable to your Unity installation:
+        Windows: C:\Program Files\Unity\Hub\Editor\6000.0.73f1\Editor\Data\Managed\UnityEngine
+        macOS:   /Applications/Unity/Hub/Editor/6000.0.73f1/Unity.app/Contents/Managed/UnityEngine
+        Linux:   ~/Unity/Hub/Editor/6000.0.73f1/Editor/Data/Managed/UnityEngine
+    -->
+    <UnityManagedPath Condition="'$(UNITY_MANAGED_PATH)' != ''">$(UNITY_MANAGED_PATH)</UnityManagedPath>
+    <UnityManagedPath Condition="'$(UnityManagedPath)' == ''">lib/UnityEngine</UnityManagedPath>
   </PropertyGroup>
+
+  <Target Name="AddUnityReferences" BeforeTargets="ResolveAssemblyReferences">
+    <ItemGroup>
+      <_UnityDll Include="$(UnityManagedPath)/*.dll" />
+      <Reference Include="%(_UnityDll.Filename)">
+        <HintPath>%(_UnityDll.FullPath)</HintPath>
+        <Private>false</Private>
+      </Reference>
+    </ItemGroup>
+  </Target>
 </Project>