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.Snowflake.Tests/Snowflake/QueryBreakdownCollectionTests.cs

@@ -188,8 +188,11 @@ public class QueryBreakdownCollectionTests
 
         // Assert
         Assert.That(summaries, Has.Count.EqualTo(2));
-        Assert.That(summaries[0].UsesSemiStructuredData, Is.True);
-        Assert.That(summaries[1].UsesStageReference, Is.True);
+        Assert.Multiple(() =>
+        {
+            Assert.That(summaries[0].UsesSemiStructuredData, Is.True);
+            Assert.That(summaries[1].UsesStageReference, Is.True);
+        });
     }
 
     [Test]
@@ -220,9 +223,12 @@ public class QueryBreakdownCollectionTests
         // Act
         _collection.AddParameterToAll("CompanyId", 99);
 
-        // Assert
-        Assert.That(_collection.QueryBreakdowns[0].Parameters["CompanyId"], Is.EqualTo(99));
-        Assert.That(_collection.QueryBreakdowns[1].Parameters["CompanyId"], Is.EqualTo(99));
+        Assert.Multiple(() =>
+        {
+            // Assert
+            Assert.That(_collection.QueryBreakdowns[0].Parameters["CompanyId"], Is.EqualTo(99));
+            Assert.That(_collection.QueryBreakdowns[1].Parameters["CompanyId"], Is.EqualTo(99));
+        });
     }
 
     [Test]