Replaced generic ASP.NET Core API guidelines in .github/copilot-instructions.md with FluentMigrator-specific migration framework patterns.

Removed:

• ASP.NET Core content (authentication, API versioning, middleware)
• Generic data access patterns irrelevant to a migration library

Added:

• Project context: 11 supported database providers (SQL Server, PostgreSQL, MySQL, SQLite, Oracle, Firebird, Snowflake, SAP HANA, Jet, Redshift, DB2)
• Migration patterns: Up()/Down() structure, AutoReversingMigration, timestamp-based versioning
• Database-agnostic code: IfDatabase() usage with ProcessorIdConstants
• Testing patterns: NUnit fixtures with Shouldly assertions, integration test organization
• Architecture: Processor/generator implementation, project structure, extension method conventions
• Build/test: dotnet build/test workflows, GitVersion integration

Example migration pattern:

[Migration(20090906205342)]
public class AddUsersTable : Migration
{
    public override void Up() =>
        Create.Table("Users")
            .WithIdColumn()
            .WithColumn("Name").AsString().NotNullable();

    public override void Down() =>
        Delete.Table("Users");
}

Retained:

• C# 13 language guidelines
• .editorconfig alignment (naming, formatting)
• Nullable reference type patterns
• XML documentation standards

• Fixes ✨ Set up Copilot instructions #2179

💡 You can make Copilot smarter by setting up custom instructions, customizing its development environment and configuring Model Context Protocol (MCP) servers. Learn more Copilot coding agent tips in the docs.