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.PostgreSql.Tests/PostgreSql/CTEColumnListTests.cs

@@ -20,9 +20,12 @@ public class CTEColumnListTests
 
         // Act & Assert
         Assert.That(withClause.ColumnList, Has.Count.EqualTo(3));
-        Assert.That(withClause.ColumnList[0], Is.EqualTo("user_id"));
-        Assert.That(withClause.ColumnList[1], Is.EqualTo("user_name"));
-        Assert.That(withClause.ColumnList[2], Is.EqualTo("user_email"));
+        Assert.Multiple(() =>
+        {
+            Assert.That(withClause.ColumnList[0], Is.EqualTo("user_id"));
+            Assert.That(withClause.ColumnList[1], Is.EqualTo("user_name"));
+            Assert.That(withClause.ColumnList[2], Is.EqualTo("user_email"));
+        });
     }
 
     [Test]
@@ -269,8 +272,11 @@ public class CTEColumnListTests
         // Assert
         Assert.That(sql, Contains.Substring("customer_transactions (trans_date, prod_id, cust_id, trans_amount, transaction_rank)"));
         var paramKeys = params_all.Keys.ToList();
-        Assert.That(paramKeys.Any(k => k.Contains("StartDate")));
-        Assert.That(paramKeys.Any(k => k.Contains("MinAmount")));
+        Assert.Multiple(() =>
+        {
+            Assert.That(paramKeys.Any(k => k.Contains("StartDate")));
+            Assert.That(paramKeys.Any(k => k.Contains("MinAmount")));
+        });
     }
 
     #endregion