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.SqlServer.Tests/Performance/GetClausesCachingTests.cs

@@ -181,8 +181,11 @@ public class GetClausesCachingTests
 
         // Assert
         Assert.That(clauses2, Is.Not.SameAs(clauses1), "GetClauses should return a new instance after ApplyClauses");
-        Assert.That(clauses2.SelectClause?.Clause, Is.EqualTo("id, name"));
-        Assert.That(clauses2.FromClause?.Clause, Is.EqualTo("customers"));
+        Assert.Multiple(() =>
+        {
+            Assert.That(clauses2.SelectClause?.Clause, Is.EqualTo("id, name"));
+            Assert.That(clauses2.FromClause?.Clause, Is.EqualTo("customers"));
+        });
     }
 
     [Test]
@@ -197,10 +200,13 @@ public class GetClausesCachingTests
 
         // Assert
         Assert.That(clauses, Is.Not.Null);
-        Assert.That(clauses.SelectClause?.Clause, Is.EqualTo("id, name"));
-        Assert.That(clauses.FromClause?.Clause, Is.EqualTo("users"));
-        Assert.That(clauses.WhereClause?.Clause, Is.EqualTo("active = 1"));
-        Assert.That(clauses.OrderByClause?.Clause, Is.EqualTo("name ASC"));
+        Assert.Multiple(() =>
+        {
+            Assert.That(clauses.SelectClause?.Clause, Is.EqualTo("id, name"));
+            Assert.That(clauses.FromClause?.Clause, Is.EqualTo("users"));
+            Assert.That(clauses.WhereClause?.Clause, Is.EqualTo("active = 1"));
+            Assert.That(clauses.OrderByClause?.Clause, Is.EqualTo("name ASC"));
+        });
     }
 
     [Test]
@@ -214,8 +220,11 @@ public class GetClausesCachingTests
         var clauses2 = query.GetClauses();
         var clauses3 = query.GetClauses();
 
-        // Assert - All should be the same instance
-        Assert.That(clauses2, Is.SameAs(clauses1));
-        Assert.That(clauses3, Is.SameAs(clauses1));
+        Assert.Multiple(() =>
+        {
+            // Assert - All should be the same instance
+            Assert.That(clauses2, Is.SameAs(clauses1));
+            Assert.That(clauses3, Is.SameAs(clauses1));
+        });
     }
 }