fix(pack): analyzer DLL path on clean machines

`mur pack-local` was failing on a freshly-cloned machine with:
  NuGet.Build.Tasks.Pack.targets(222,5): error
  Could not find a part of the path
    '...\src\Reactor.Analyzers\bin\Debug\netstandard2.0\'

Root cause: Reactor.csproj packs the analyzer + localization-generator
DLLs into the framework nupkg via `<None Include>` paths that hardcode
`bin\$(Configuration)\netstandard2.0\` — no `$(Platform)` segment. The
two projects are also `<ProjectReference>`s, so when `dotnet pack` is
invoked with `-p:Platform=x64` (or ARM64) the inherited Platform
cascades to the transitive analyzer build and the output actually
lands at `bin\x64\Debug\netstandard2.0\`. Pack then looks at the
platform-less path, doesn't find the file, and fails.

The bug was masked on dev machines by any prior AnyCPU build (VS
solution, bare `dotnet build src/Reactor.Analyzers`, etc.) that left
a stale DLL at the platform-less path.

Fix: set `AppendPlatformToOutputPath=false` on both analyzer csprojs.
These are netstandard2.0 IL with no platform-specific code, so output
should always land at `bin\$(Configuration)\netstandard2.0\` regardless
of what Platform the parent pack invocation inherited.

Reproduced + verified locally with a wiped bin/obj tree.

Co-Authored-By: Claude Opus 4.7 (1M context) <noreply@anthropic.com>

Author: codemonkeychris

src/Reactor.Analyzers/Reactor.Analyzers.csproj

@@ -12,6 +12,17 @@
     <!-- Bundled into Microsoft.UI.Reactor.nupkg — does not ship as its own
          package. See docs/specs/022-packaging-and-distribution.md §5. -->
     <IsPackable>false</IsPackable>
+
+    <!-- Analyzers are platform-independent netstandard2.0 IL. Without this,
+         when Reactor.csproj is packed with `-p:Platform=x64` (or ARM64) the
+         inherited Platform cascades into this transitive build and the
+         output lands at bin\x64\Debug\netstandard2.0\ — but Reactor.csproj's
+         <None Include="...\bin\$(Configuration)\netstandard2.0\..."> for
+         packing the analyzer DLL has no $(Platform) segment and breaks pack
+         on a clean machine (no prior AnyCPU build to fall back to).
+         AppendPlatformToOutputPath=false pins us to bin\$(Configuration)\
+         regardless of inherited Platform. -->
+    <AppendPlatformToOutputPath>false</AppendPlatformToOutputPath>
   </PropertyGroup>
 
   <ItemGroup>

src/Reactor.Localization.Generator/Reactor.Localization.Generator.csproj

@@ -9,6 +9,12 @@
     <IsRoslynComponent>true</IsRoslynComponent>
     <RootNamespace>Microsoft.UI.Reactor.Localization.Generator</RootNamespace>
     <AssemblyName>Reactor.Localization.Generator</AssemblyName>
+
+    <!-- See Reactor.Analyzers.csproj for the full rationale: Reactor.csproj's
+         <None Include="...\bin\$(Configuration)\netstandard2.0\..."> pack
+         glob has no $(Platform) segment, so this transitive source-generator
+         build must not append the inherited Platform to its OutputPath. -->
+    <AppendPlatformToOutputPath>false</AppendPlatformToOutputPath>
   </PropertyGroup>
 
   <ItemGroup>