Add comprehensive Copilot coding agent instructions for BCApps repository

[Copilot]

This PR adds a comprehensive .github/copilot-instructions.md file to onboard coding agents to the BCApps repository, enabling them to work more efficiently and reduce the likelihood of build failures or rejected pull requests.

Overview

The BCApps repository is a specialized Microsoft Dynamics 365 Business Central application codebase using the AL (Application Language) and AL-Go framework. This presents unique challenges for coding agents unfamiliar with this ecosystem, as it differs significantly from typical web development or .NET projects.

Key Information Provided

Repository Structure & Scale:

• 3,290+ AL files, 45MB of source code
• AL-Go framework (Microsoft's AL development automation)
• Windows-only development environment
• 7 buildable AL-Go projects (System Application, Business Foundation, Developer Tools)

Critical Build Requirements:

• Docker Desktop with Windows containers (not Linux)
• PowerShell (not bash) for all build operations
• BCContainerHelper module for Business Central container management
• Container-based development environment

Build Process Documentation:

# Example: Build System Application
.\build.ps1 -ALGoProject "System Application" -AutoFill

# Example: Setup development environment
.\build\scripts\DevEnv\NewDevEnv.ps1 -ContainerName 'BCApps-Dev'

Common Pitfalls Addressed:

• Attempting to use standard npm/dotnet build patterns (AL-Go is required)
• Using bash instead of PowerShell for builds
• Running Linux containers instead of Windows containers
• Missing GitHub issue links (PRs are auto-rejected without approved issues)

Benefits for Coding Agents

This documentation will significantly reduce:

• Time spent exploring the codebase structure
• Build failures due to incorrect environment setup
• PR rejections due to missing requirements or validation failures
• Need for trial-and-error with build commands

The instructions follow the specified format with repository overview, build requirements, project layout, and explicit guidance to trust the instructions rather than searching when the provided information is complete.

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