chore(sonar)!: mark Markdown generator classes as 'public static class' (S1118)

After the CA1822 cascade in #15 left every method on the eight
Markdown generator classes static, the classes themselves were
instantiable shells that consumers couldn't usefully `new`. This
commit flips the `class` modifier to `static class` on all eight:

- `Markdown.SqlServer.QueryBreakdownGenerator`
- `Markdown.SqlServer.SqlStatementGenerator`
- `Markdown.LinqToSql.QueryBreakdownGenerator`
- `Markdown.LinqToSql.SqlStatementGenerator`
- `Markdown.PostgreSql.QueryBreakdownGenerator`
- `Markdown.PostgreSql.SqlStatementGenerator`
- `Markdown.Snowflake.QueryBreakdownGenerator`
- `Markdown.Snowflake.SqlStatementGenerator`

Test fixtures drop the now-meaningless `_generator = new …()` field
and `[SetUp]` (kept the existing Setup body where unrelated state was
also initialized — `QueryMarkdownGenerationTests` and
`LinqToSql.QueryBreakdownGeneratorTests`).

BREAKING CHANGE: External NuGet consumers can no longer write
`new Markdown.Snowflake.SqlStatementGenerator()` (or any of the other
seven classes above) — the type is now a static container and may only
be referenced by name, e.g.
`Markdown.Snowflake.SqlStatementGenerator.GenerateSequenceDiagram(…)`.
The call syntax for the static methods is unchanged.

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

src/Strata.SqlTools.Markdown/LinqToSql/QueryBreakdownGenerator.cs

@@ -6,7 +6,7 @@ namespace Strata.SqlTools.Markdown.LinqToSql;
 /// Generates Mermaid diagram markdown from LINQ to SQL QueryBreakdown objects.
 /// Creates flowchart visualizations showing the LINQ query structure and flow.
 /// </summary>
-public class QueryBreakdownGenerator
+public static class QueryBreakdownGenerator
 {
     /// <summary>
     /// Generates a Mermaid flowchart diagram from a LINQ to SQL QueryBreakdown.

src/Strata.SqlTools.Markdown/LinqToSql/SqlStatementGenerator.cs

@@ -8,7 +8,7 @@ namespace Strata.SqlTools.Markdown.LinqToSql;
 /// Generates Mermaid diagrams for LINQ to SQL statements, including sequence diagrams
 /// for statement execution flow and entity-relationship diagrams.
 /// </summary>
-public class SqlStatementGenerator
+public static class SqlStatementGenerator
 {
     /// <summary>
     /// Generates a Mermaid sequence diagram showing LINQ to SQL statement execution flow.

src/Strata.SqlTools.Markdown/PostgreSql/QueryBreakdownGenerator.cs

@@ -6,7 +6,7 @@ namespace Strata.SqlTools.Markdown.PostgreSql;
 /// Generates Mermaid diagram markdown from PostgreSQL SQL QueryBreakdown objects.
 /// Creates flowchart visualizations showing the query structure and flow.
 /// </summary>
-public class QueryBreakdownGenerator
+public static class QueryBreakdownGenerator
 {
     /// <summary>
     /// Generates a Mermaid flowchart diagram from a PostgreSQL QueryBreakdown.

src/Strata.SqlTools.Markdown/PostgreSql/SqlStatementGenerator.cs

@@ -6,7 +6,7 @@ namespace Strata.SqlTools.Markdown.PostgreSql;
 /// Generates Mermaid diagrams for PostgreSQL SQL statements, including sequence diagrams
 /// for statement execution flow and entity-relationship diagrams.
 /// </summary>
-public class SqlStatementGenerator
+public static class SqlStatementGenerator
 {
     /// <summary>
     /// Generates a Mermaid sequence diagram showing PostgreSQL SQL statement execution flow.

src/Strata.SqlTools.Markdown/Snowflake/QueryBreakdownGenerator.cs

@@ -6,7 +6,7 @@ namespace Strata.SqlTools.Markdown.Snowflake;
 /// Generates Mermaid diagram markdown from Snowflake SQL QueryBreakdown objects.
 /// Creates flowchart visualizations showing the query structure and flow.
 /// </summary>
-public class QueryBreakdownGenerator
+public static class QueryBreakdownGenerator
 {
     /// <summary>
     /// Generates a Mermaid flowchart diagram from a Snowflake QueryBreakdown.

src/Strata.SqlTools.Markdown/Snowflake/SqlStatementGenerator.cs

@@ -6,7 +6,7 @@ namespace Strata.SqlTools.Markdown.Snowflake;
 /// Generates Mermaid diagrams for Snowflake SQL statements, including sequence diagrams
 /// for statement execution flow and entity-relationship diagrams.
 /// </summary>
-public class SqlStatementGenerator
+public static class SqlStatementGenerator
 {
     /// <summary>
     /// Generates a Mermaid sequence diagram showing Snowflake SQL statement execution flow.

src/Strata.SqlTools.Markdown/SqlServer/QueryBreakdownGenerator.cs

@@ -8,7 +8,7 @@ namespace Strata.SqlTools.Markdown.SqlServer;
 /// Generates Mermaid diagram markdown from SQL QueryBreakdown objects.
 /// Creates flowchart visualizations showing the query structure and flow.
 /// </summary>
-public class QueryBreakdownGenerator
+public static class QueryBreakdownGenerator
 {
     /// <summary>
     /// Generates a Mermaid flowchart diagram from a QueryBreakdown.

src/Strata.SqlTools.Markdown/SqlServer/SqlStatementGenerator.cs

@@ -6,7 +6,7 @@ namespace Strata.SqlTools.Markdown.SqlServer;
 /// <summary>
 /// Generates Mermaid sequence diagrams from SQL statements to visualize statement execution flow.
 /// </summary>
-public class SqlStatementGenerator
+public static class SqlStatementGenerator
 {
     /// <summary>
     /// Generates a Mermaid sequence diagram showing SQL statement execution.

tests/Strata.SqlTools.Markdown.Tests/LinqToSql/QueryBreakdownGeneratorTests.cs

@@ -6,13 +6,11 @@ namespace Strata.SqlTools.Markdown.Tests.LinqToSql;
 [TestFixture]
 public class QueryBreakdownGeneratorTests
 {
-    private QueryBreakdownGenerator _generator = null!;
     private TestDataContext _context = null!;
 
     [SetUp]
     public void Setup()
     {
-        _generator = new QueryBreakdownGenerator();
         _context = new TestDataContext();
     }
 

tests/Strata.SqlTools.Markdown.Tests/LinqToSql/SqlStatementGeneratorTests.cs

@@ -6,14 +6,6 @@ namespace Strata.SqlTools.Markdown.Tests.LinqToSql;
 [TestFixture]
 public class SqlStatementGeneratorTests
 {
-    private SqlStatementGenerator _generator = null!;
-
-    [SetUp]
-    public void Setup()
-    {
-        _generator = new SqlStatementGenerator();
-    }
-
     [Test]
     public void GenerateLinqPipelineDiagram_BasicQuery_GeneratesSequenceDiagram()
     {

tests/Strata.SqlTools.Markdown.Tests/PostgreSql/QueryBreakdownGeneratorTests.cs

@@ -6,14 +6,6 @@ namespace Strata.SqlTools.Markdown.Tests.PostgreSql;
 [TestFixture]
 public class QueryBreakdownGeneratorTests
 {
-    private QueryBreakdownGenerator _generator = null!;
-
-    [SetUp]
-    public void Setup()
-    {
-        _generator = new QueryBreakdownGenerator();
-    }
-
     [Test]
     public void GenerateMermaidDiagram_SimplePostgreSqlQuery_GeneratesValidMermaid()
     {

tests/Strata.SqlTools.Markdown.Tests/PostgreSql/SqlStatementGeneratorTests.cs

@@ -6,14 +6,6 @@ namespace Strata.SqlTools.Markdown.Tests.PostgreSql;
 [TestFixture]
 public class SqlStatementGeneratorTests
 {
-    private SqlStatementGenerator _generator = null!;
-
-    [SetUp]
-    public void Setup()
-    {
-        _generator = new SqlStatementGenerator();
-    }
-
     [Test]
     public void GenerateSequenceDiagram_PostgreSqlQuery_GeneratesValidDiagram()
     {

tests/Strata.SqlTools.Markdown.Tests/Snowflake/QueryBreakdownGeneratorTests.cs

@@ -6,14 +6,6 @@ namespace Strata.SqlTools.Markdown.Tests.Snowflake;
 [TestFixture]
 public class QueryBreakdownGeneratorTests
 {
-    private QueryBreakdownGenerator _generator = null!;
-
-    [SetUp]
-    public void Setup()
-    {
-        _generator = new QueryBreakdownGenerator();
-    }
-
     [Test]
     public void GenerateMermaidDiagram_SimpleSnowflakeQuery_GeneratesValidMermaid()
     {

tests/Strata.SqlTools.Markdown.Tests/Snowflake/SqlStatementGeneratorTests.cs

@@ -6,14 +6,6 @@ namespace Strata.SqlTools.Markdown.Tests.Snowflake;
 [TestFixture]
 public class SqlStatementGeneratorTests
 {
-    private SqlStatementGenerator _generator = null!;
-
-    [SetUp]
-    public void Setup()
-    {
-        _generator = new SqlStatementGenerator();
-    }
-
     [Test]
     public void GenerateSequenceDiagram_SnowflakeQuery_GeneratesValidDiagram()
     {

tests/Strata.SqlTools.Markdown.Tests/SqlServer/QueryBreakdownGeneratorTests.cs

@@ -7,14 +7,6 @@ namespace Strata.SqlTools.Markdown.Tests.SqlServer;
 [TestFixture]
 public class QueryBreakdownGeneratorTests
 {
-    private QueryBreakdownGenerator _generator = null!;
-
-    [SetUp]
-    public void Setup()
-    {
-        _generator = new QueryBreakdownGenerator();
-    }
-
     [Test]
     public void GenerateMermaidDiagram_WithSimpleQuery_GeneratesFlowchart()
     {

tests/Strata.SqlTools.Markdown.Tests/SqlServer/QueryMarkdownGenerationTests.cs

@@ -8,15 +8,12 @@ namespace Strata.SqlTools.Markdown.Tests.SqlServer;
 [Category("MarkdownGeneration")]
 public class QueryMarkdownGenerationTests
 {
-    private QueryBreakdownGenerator _generator = null!;
     private string _queriesSourcePath = null!;
     private string _markdownOutputPath = null!;
 
     [SetUp]
     public void Setup()
     {
-        _generator = new QueryBreakdownGenerator();
-
         // Get the solution root directory
         var testDirectory = TestContext.CurrentContext.TestDirectory;
         var solutionRoot = Directory.GetParent(testDirectory)?.Parent?.Parent?.Parent?.Parent?.FullName;

tests/Strata.SqlTools.Markdown.Tests/SqlServer/SqlStatementGeneratorTests.cs

@@ -6,14 +6,6 @@ namespace Strata.SqlTools.Markdown.Tests.SqlServer;
 [TestFixture]
 public class SqlStatementGeneratorTests
 {
-    private SqlStatementGenerator _generator = null!;
-
-    [SetUp]
-    public void Setup()
-    {
-        _generator = new SqlStatementGenerator();
-    }
-
     [Test]
     public void GenerateSequenceDiagram_WithSimpleQuery_GeneratesSequence()
     {