feat(mssql): add MSSQL writer for generating DDL from database schema

- Implement MSSQL writer to generate SQL scripts for creating schemas, tables, and constraints.
- Support for identity columns, indexes, and extended properties.
- Add tests for column definitions, table creation, primary keys, foreign keys, and comments.
- Include testing guide and sample schema for integration tests.

CLAUDE.md

@@ -6,9 +6,9 @@ This file provides guidance to Claude Code (claude.ai/code) when working with co
 
 RelSpec is a database relations specification tool that provides bidirectional conversion between various database schema formats. It reads database schemas from multiple sources and writes them to various formats.
 
-**Supported Readers:** Bun, DBML, DCTX, DrawDB, Drizzle, GORM, GraphQL, JSON, PostgreSQL, Prisma, SQL Directory, SQLite, TypeORM, YAML
+**Supported Readers:** Bun, DBML, DCTX, DrawDB, Drizzle, GORM, GraphQL, JSON, MSSQL, PostgreSQL, Prisma, SQL Directory, SQLite, TypeORM, YAML
 
-**Supported Writers:** Bun, DBML, DCTX, DrawDB, Drizzle, GORM, GraphQL, JSON, PostgreSQL, Prisma, SQL Exec, SQLite, Template, TypeORM, YAML
+**Supported Writers:** Bun, DBML, DCTX, DrawDB, Drizzle, GORM, GraphQL, JSON, MSSQL, PostgreSQL, Prisma, SQL Exec, SQLite, Template, TypeORM, YAML
 
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