docs: enhance copilot instructions with detailed architecture patterns

[kevwan]

Description

This PR enhances the file to provide AI coding agents with comprehensive knowledge about the go-zero framework's architecture, patterns, and conventions.

Changes

Architecture Overview

• Added Gateway component documentation for API gateway functionality
• Added MCP Server component for AI agent integration via SSE
• Expanded core utilities documentation with specific categories:
  • Resilience: circuit breakers, rate limiters, adaptive load shedding
  • Storage: SQL with cache, Redis, MongoDB
  • Concurrency: MapReduce, worker pools, sync primitives
  • Observability: metrics, tracing, structured logging

Configuration Patterns

• Documented the requirement to embed service.ServiceConf in all service configs
• Added service modes documentation (dev/test/rt vs pre/pro)
• Clarified impact of modes on system protections (load shedding, stats)

Framework Guidelines

• REST API: Added middleware chain architecture with Append()/Prepend() methods
• RPC: Documented p2c_ewma load balancing, health checks, and client configuration
• Database: Explained cache-aside pattern with CachedConn and connection pooling details

Build Commands

• Added comprehensive goctl code generation commands:
  • REST API generation
  • RPC service generation
  • Database model generation from SQL

New Section: Critical Architecture Patterns

• Resilience Design Philosophy: Defense-in-depth approach with 4 protection layers
• Middleware Chain Architecture: Composition patterns with code examples
• Concurrency Patterns: MapReduce, Executors, and SingleFlight use cases

Benefits

These enhancements help AI coding agents:

• Understand the "why" behind architectural decisions
• Follow project-specific conventions that differ from common practices
• Execute critical workflows (goctl commands) that aren't obvious from file inspection
• Grasp integration points and cross-component communication patterns

Testing

• Documentation changes only, no code modifications
• Verified markdown formatting
• Ensured all code examples use correct syntax

cc @kevwan

[Copilot]

Pull request overview

This PR significantly enhances the Copilot instructions documentation to provide AI coding agents with comprehensive knowledge about go-zero's architecture, patterns, and conventions.

Key Changes:

• Expanded architecture component descriptions with specific package paths and detailed functionality
• Added new Gateway and MCP Server components documentation
• Enhanced configuration patterns with service mode behavior and struct embedding guidelines
• Documented critical architecture patterns including resilience design philosophy, middleware chain architecture, and concurrency patterns