chore(sonar)!: cascade CA1822 through Markdown dialect wrappers

Commit 5202d93 made the SqlServer-namespaced Markdown generator methods
static, which left the LinqToSql / PostgreSql / Snowflake wrapper
classes' instance methods delegating to nothing but a static call.
SonarQube re-flagged those 10 wrapper methods as CA1822 on the next
scan.

This sweep:

- Makes all 10 wrapper instance methods `static` (`dotnet format` driven).
- Makes `Markdown.LinqToSql.QueryBreakdownGenerator.GenerateCombinedDiagram`
  static preemptively — it composes two static helpers and would otherwise
  be the next-iteration cascade flag.
- Removes the now-dead `_baseGenerator` field and its initializing
  constructor from all six dialect wrappers (LinqToSql / PostgreSql /
  Snowflake × QueryBreakdownGenerator + SqlStatementGenerator). The
  classes keep their implicit parameterless constructor so `new
  Snowflake.QueryBreakdownGenerator()` still compiles.
- Updates the one test call site (`GenerateCombinedDiagram`) the fixer
  didn't catch to use type-name form.

BREAKING CHANGE: External NuGet consumers calling
`instance.Generate*Diagram(...)` on `Markdown.LinqToSql.*`,
`Markdown.PostgreSql.*`, or `Markdown.Snowflake.*` generators must
switch to type-name form, e.g. `Markdown.Snowflake.SqlStatementGenerator.GenerateSequenceDiagram(...)`.
The class types and parameterless constructors remain — only the call
syntax for these methods changes.

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

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

@@ -25,7 +25,7 @@ public class SqlStatementGeneratorTests
         ", isMicrosoftSql: false);
 
         // Act
-        var result = _generator.GenerateSequenceDiagram(query, "User Query Flow");
+        var result = SqlStatementGenerator.GenerateSequenceDiagram(query, "User Query Flow");
 
         // Assert
         Assert.That(result, Does.Contain("```mermaid"));
@@ -51,7 +51,7 @@ public class SqlStatementGeneratorTests
         ", isMicrosoftSql: false);
 
         // Act
-        var result = _generator.GenerateSequenceDiagram(query);
+        var result = SqlStatementGenerator.GenerateSequenceDiagram(query);
 
         // Assert
         Assert.That(result, Does.Contain("Execute Main Statement"));
@@ -73,7 +73,7 @@ public class SqlStatementGeneratorTests
         ", isMicrosoftSql: false);
 
         // Act
-        var result = _generator.GenerateSequenceDiagram(query, "Sales Analysis");
+        var result = SqlStatementGenerator.GenerateSequenceDiagram(query, "Sales Analysis");
 
         // Assert
         Assert.That(result, Does.Contain("### Sales Analysis"));
@@ -90,7 +90,7 @@ public class SqlStatementGeneratorTests
         var tables = new[] { "CUSTOMERS", "ORDERS", "ORDER_ITEMS", "PRODUCTS" };
 
         // Act
-        var result = _generator.GenerateEntityRelationshipDiagram(tables, "E-Commerce Schema");
+        var result = SqlStatementGenerator.GenerateEntityRelationshipDiagram(tables, "E-Commerce Schema");
 
         // Assert
         Assert.That(result, Does.Contain("```mermaid"));
@@ -109,7 +109,7 @@ public class SqlStatementGeneratorTests
         var tables = new[] { "\"customers\"", "\"orders\"", "\"orderItems\"" };
 
         // Act
-        var result = _generator.GenerateEntityRelationshipDiagram(tables);
+        var result = SqlStatementGenerator.GenerateEntityRelationshipDiagram(tables);
 
         // Assert
         Assert.That(result, Does.Contain("erDiagram"));
@@ -123,7 +123,7 @@ public class SqlStatementGeneratorTests
         var tables = new[] { "USERS" };
 
         // Act
-        var result = _generator.GenerateEntityRelationshipDiagram(tables);
+        var result = SqlStatementGenerator.GenerateEntityRelationshipDiagram(tables);
 
         // Assert
         Assert.That(result, Does.Contain("erDiagram"));
@@ -137,7 +137,7 @@ public class SqlStatementGeneratorTests
         var query = new QueryBreakdown("ORDER_ID", "ORDERS");
 
         // Act
-        var result = _generator.GenerateSequenceDiagram(query, null);
+        var result = SqlStatementGenerator.GenerateSequenceDiagram(query, null);
 
         // Assert
         Assert.That(result, Does.Not.Contain("###"));