Add comprehensive GitHub Copilot instructions for IdentityManager.LogInsights

[Copilot]

This PR adds a comprehensive .github/copilot-instructions.md file that provides GitHub Copilot coding agents with detailed instructions on how to work effectively with the IdentityManager.LogInsights codebase.

What's Included

The instructions cover all essential aspects for working with this .NET 8 Windows Forms application:

Platform & Build Requirements:

• Clear documentation that this is a Windows-only application due to Windows Forms dependencies
• Exact commands for building (dotnet build) and running the application
• Explicit timeout warnings ("NEVER CANCEL") with recommended values for build operations

Project Architecture:

• Detailed breakdown of the project structure and key components
• Component dependency mapping for the detector system
• Important file locations and their purposes

Development Guidelines:

• Manual validation requirements (no automated tests exist)
• Essential test scenarios for validating changes
• Code style guidelines and performance considerations
• Error handling patterns used throughout the application

Key Components Documentation:

• Detectors: Log analysis components with dependency hierarchy
• LogReader: Implementations for different log sources (files, Azure Application Insights)
• UI Controls: Custom Windows Forms components
• Core Classes: Main application logic and data structures

The instructions use an imperative tone throughout ("Run this command", "Do not do this") and emphasize the critical requirement for manual testing since no automated test infrastructure exists. They also include specific timeout values and cancellation warnings for build operations that may take several minutes.

This will enable GitHub Copilot agents to work efficiently with the codebase while understanding the platform constraints and validation requirements specific to this Windows Forms log analysis application.

Fixes #177.

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[joergrosenkranz]

@copilot Check if the content is still relevant for copilot-instructions