chore: track public API surface

Author: thomhurst

CONTRIBUTING.md

@@ -0,0 +1,14 @@
+# Contributing
+
+## Public API changes
+
+`Microsoft.CodeAnalysis.PublicApiAnalyzers` tracks the library's public surface. A build fails when public members change without a matching baseline update.
+
+For an intentional API change:
+
+1. Add new declarations to `EnumerableAsyncProcessor/PublicAPI.Unshipped.txt`.
+2. Prefix removed declarations with `*REMOVED*` in `PublicAPI.Unshipped.txt`.
+3. Include the baseline changes in the same pull request as the code change so reviewers can inspect the public API diff.
+4. Move approved declarations from `PublicAPI.Unshipped.txt` to `PublicAPI.Shipped.txt` when preparing a release. Keep `#nullable enable` as the first line in both files.
+
+Run `dotnet build` to verify the baseline on every target framework.

EnumerableAsyncProcessor/EnumerableAsyncProcessor.csproj

@@ -6,6 +6,9 @@
         <Nullable>enable</Nullable>
         <LangVersion>latest</LangVersion>
         <Version>99.99.99</Version>
+        <WarningsAsErrors>$(WarningsAsErrors);RS0016;RS0017</WarningsAsErrors>
+        <!-- Existing overload families intentionally retain optional parameters. -->
+        <NoWarn>$(NoWarn);RS0026</NoWarn>
     </PropertyGroup>
 
     <PropertyGroup>
@@ -30,9 +33,15 @@
 
         <PackageReference Include="Microsoft.SourceLink.GitHub" Version="10.0.301" PrivateAssets="All"/>
         <PackageReference Include="System.Threading.RateLimiting" Version="10.0.10" />
+        <PackageReference Include="Microsoft.CodeAnalysis.PublicApiAnalyzers" Version="5.6.0" PrivateAssets="All" />
 
     </ItemGroup>
 
+    <ItemGroup>
+        <AdditionalFiles Include="PublicAPI.Shipped.txt" />
+        <AdditionalFiles Include="PublicAPI.Unshipped.txt" />
+    </ItemGroup>
+
     <PropertyGroup>
         <Authors>Tom Longhurst</Authors>
         <Description>Various Enumerable Async Processors - Batch / Parallel / Rate Limited / One at a time</Description>