Replace FluentAssertions with Shouldly

- Remove FluentAssertions package reference
- Add Shouldly 4.3.0 package
- Update test assertions to use Shouldly syntax:
  - true.Should().BeTrue() → true.ShouldBeTrue()
  - result.Should().Be(expected) → result.ShouldBe(expected)
- All tests pass (4 passed, 1 skipped)

🤖 Generated with [Claude Code](https://claude.com/claude-code)

Co-Authored-By: Claude <noreply@anthropic.com>

Author: StevenTCramer

Directory.Packages.props

@@ -9,6 +9,7 @@
     <PackageVersion Include="Microsoft.Extensions.DependencyInjection.Abstractions" Version="9.0.10" />
     <PackageVersion Include="Microsoft.Extensions.Logging.Abstractions" Version="9.0.10" />
     <PackageVersion Include="Microsoft.Extensions.Options.ConfigurationExtensions" Version="9.0.10" />
+    <PackageVersion Include="Shouldly" Version="4.3.0" />
     <PackageVersion Include="TimeWarp.Build.Tasks" Version="1.0.0">
       <IncludeAssets>runtime; build; native; contentfiles; analyzers; buildtransitive</IncludeAssets>
       <PrivateAssets>all</PrivateAssets>

tests/timewarp-options-validation-tests/convention-tests.cs

@@ -1,24 +1,24 @@
 namespace ConventionTest_;
 
-using FluentAssertions;
+using Shouldly;
 using TimeWarp.Fixie;
 
 [TestTag(TestTags.Fast)]
 public class SimpleNoApplicationTest_Should_
 {
-  public static void AlwaysPass() => true.Should().BeTrue();
+  public static void AlwaysPass() => true.ShouldBeTrue();
 
   [Skip("Demonstrates skip attribute")]
-  public static void SkipExample() => true.Should().BeFalse();
+  public static void SkipExample() => true.ShouldBeFalse();
 
   [TestTag(TestTags.Fast)]
-  public static void TagExample() => true.Should().BeTrue();
+  public static void TagExample() => true.ShouldBeTrue();
 
   [Input(5, 3, 2)]
   [Input(8, 5, 3)]
   public static void Subtract(int aX, int aY, int aExpectedDifference)
   {
     int result = aX - aY;
-    result.Should().Be(aExpectedDifference);
+    result.ShouldBe(aExpectedDifference);
   }
 }

tests/timewarp-options-validation-tests/timewarp-options-validation-tests.csproj

@@ -6,7 +6,7 @@
 
   <ItemGroup>
     <PackageReference Include="Fixie.TestAdapter" />
-    <PackageReference Include="FluentAssertions" />
+    <PackageReference Include="Shouldly" />
     <PackageReference Include="TimeWarp.Fixie" />
   </ItemGroup>