Remove redundant null-forgiving operators

Eliminated unnecessary null-forgiving operators in DiffToolsTest assertions (e.g. changed tool1!.Name to tool1.Name across several asserts). Also added the missing newline at end of file. Minor cleanup to improve readability and align with nullable analysis.

Author: SimonCropp

src/DiffEngine.Tests/DiffToolsTest.cs

@@ -237,19 +237,19 @@ public void TryFindByName_IsCaseInsensitive()
 
         // Exact case
         Assert.True(DiffTools.TryFindByName("MyCaseSensitiveTool", out var tool1));
-        Assert.Equal("MyCaseSensitiveTool", tool1!.Name);
+        Assert.Equal("MyCaseSensitiveTool", tool1.Name);
 
         // All lowercase
         Assert.True(DiffTools.TryFindByName("mycasesensitivetool", out var tool2));
-        Assert.Equal("MyCaseSensitiveTool", tool2!.Name);
+        Assert.Equal("MyCaseSensitiveTool", tool2.Name);
 
         // All uppercase
         Assert.True(DiffTools.TryFindByName("MYCASESENSITIVETOOL", out var tool3));
-        Assert.Equal("MyCaseSensitiveTool", tool3!.Name);
+        Assert.Equal("MyCaseSensitiveTool", tool3.Name);
 
         // Mixed case
         Assert.True(DiffTools.TryFindByName("myCASEsensitiveTOOL", out var tool4));
-        Assert.Equal("MyCaseSensitiveTool", tool4!.Name);
+        Assert.Equal("MyCaseSensitiveTool", tool4.Name);
     }
 
     [Fact]
@@ -291,4 +291,4 @@ public void AddTool_RejectsDuplicateNameCaseInsensitive()
     public DiffToolsTest(ITestOutputHelper output) :
         base(output) =>
         DiffTools.Reset();
-}
+}