Enable package validation for the MCP extension packages

ModelContextProtocol.Extensions.Apps and ModelContextProtocol.Extensions.Tasks
both opted out of package validation with EnablePackageValidation=false and the
comment "New package with no published baseline yet". That is no longer true:
both packages have shipped 2.0.0 and 2.1.0 on NuGet.org, so the central
PackageValidationBaselineVersion of 2.0.0 in src/Directory.Build.props now
resolves for them just like it does for the other three shipping packages.

Removing the opt-out means these packages get the same ApiCompat
breaking-change detection as ModelContextProtocol.Core, ModelContextProtocol,
and ModelContextProtocol.AspNetCore. Verified with a clean Release pack: both
packages validate against their 2.0.0 baselines with zero diagnostics, so no
suppression file is needed for either.

Co-authored-by: Copilot App <223556219+Copilot@users.noreply.github.com>

Author: jeffhandley

src/ModelContextProtocol.Extensions.Apps/ModelContextProtocol.Extensions.Apps.csproj

@@ -9,8 +9,6 @@
     <PackageReadmeFile>README.md</PackageReadmeFile>
     <!-- Suppress the experimental MCP warnings for internal usage -->
     <NoWarn>$(NoWarn);MCPEXP001;MCPEXP003</NoWarn>
-    <!-- New package with no published baseline yet -->
-    <EnablePackageValidation>false</EnablePackageValidation>
   </PropertyGroup>
 
   <PropertyGroup Condition="'$(TargetFramework)' != 'netstandard2.0'">

src/ModelContextProtocol.Extensions.Tasks/ModelContextProtocol.Extensions.Tasks.csproj

@@ -9,8 +9,6 @@
     <PackageReadmeFile>README.md</PackageReadmeFile>
     <!-- Suppress the experimental MCP warnings for internal usage -->
     <NoWarn>$(NoWarn);MCPEXP001;MCPEXP002</NoWarn>
-    <!-- New package with no published baseline yet -->
-    <EnablePackageValidation>false</EnablePackageValidation>
   </PropertyGroup>
 
   <PropertyGroup Condition="'$(TargetFramework)' != 'netstandard2.0'">