chore(sonar): wrap independent assertions in Assert.Multiple (NUnit2045)

Driven by `dotnet format analyzers --diagnostics NUnit2045`. The fixer
groups consecutive independent `Assert.That(...)` calls into
`Assert.Multiple(() => { ... })`, so a failing assertion no longer
short-circuits the block — every failure inside the group is reported,
which gives much better diagnostics on multi-property tests.

Audit confirmed no Assert.Throws / Assert.Fail / Assert.Catch / Assert.Pass
/ Assert.DoesNotThrow got pulled inside a Multiple block (those need to
short-circuit). All 1180 tests pass.

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

tests/Strata.SqlTools.EFCore.Tests/QueryBreakdownRepositoryTests.cs

@@ -58,8 +58,11 @@ public class QueryBreakdownRepositoryTests
 
         // Assert
         Assert.That(retrieved, Is.Not.Null);
-        Assert.That(retrieved?.SelectClause?.Clause, Is.EqualTo("ID, Name"));
-        Assert.That(retrieved?.FromClause?.Clause, Is.EqualTo("Users"));
+        Assert.Multiple(() =>
+        {
+            Assert.That(retrieved?.SelectClause?.Clause, Is.EqualTo("ID, Name"));
+            Assert.That(retrieved?.FromClause?.Clause, Is.EqualTo("Users"));
+        });
     }
 
     [Test]
@@ -117,9 +120,12 @@ public class QueryBreakdownRepositoryTests
         bool deleted = await _repository.DeleteAsync(id);
         var retrieved = await _repository.GetByIdAsync(id);
 
-        // Assert
-        Assert.That(deleted, Is.True);
-        Assert.That(retrieved, Is.Null);
+        Assert.Multiple(() =>
+        {
+            // Assert
+            Assert.That(deleted, Is.True);
+            Assert.That(retrieved, Is.Null);
+        });
     }
 
     [Test]