Add comprehensive GitHub Copilot instructions for development workflow

[Copilot]

Created a comprehensive .github/copilot-instructions.md file that provides GitHub Copilot coding agents with detailed instructions for working effectively in this .NET source generator codebase.

Key Features

Prerequisites & Setup: Exact installation commands for all required dependencies:

• .NET 9.0.200 SDK and .NET 9.0 runtime installation via dotnet-install script
• Bun package manager for JavaScript tooling and version management
• Proper environment variable configuration (DOTNET_ROOT, PATH)

Validated Build & Test Commands: All commands have been tested and include measured timing:

• make build - builds source generator and integration tests (26 seconds)
• make test - runs 282 integration tests (42 seconds)
• make format - code formatting with .editorconfig rules (21 seconds)
• Sample application build and test commands (19 seconds + 3 seconds)

Critical Timeout Warnings: Explicit "NEVER CANCEL" warnings with recommended timeout values:

• Build operations: 60+ minute timeouts
• Test operations: 60+ minute timeouts
• Formatting operations: 30+ minute timeouts

Functional Validation Requirements: Specific scenarios for testing source generator changes:

• ActivitySource generation validation
• ILogger generation validation
• Metrics generation validation
• Integration with sample .NET Aspire application
• Generated code inspection in obj/generated/ directories

Project Architecture Documentation: Complete structure overview including:

• Main source generator library (src/Purview.Telemetry.SourceGenerator/)
• 282 integration tests with snapshot testing
• .NET Aspire sample application demonstrating telemetry integration
• Build system using Makefile, Bun, and .slnx solution files

The instructions emphasize exhaustive validation, proper timing expectations, and functional testing to ensure source generator changes work correctly end-to-end.

Fixes #79.

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[Copilot]

@kieronlanning 👋 This repository doesn't have Copilot instructions. With Copilot instructions, I can understand the repository better, work faster and produce higher quality PRs.

I can generate a .github/copilot-instructions.md file for you automatically. Click here to open a pre-filled issue and assign it to me. I'll write the instructions, and then tag you for review.

[Copilot]

Pull Request Overview

This PR adds comprehensive development workflow instructions for GitHub Copilot coding agents working with the Purview Telemetry Source Generator codebase. The instructions provide detailed guidance on prerequisites, build processes, testing procedures, and project architecture to help AI agents work effectively in this .NET source generator project.

Key changes:

• Added complete setup and prerequisite instructions with exact installation commands
• Documented all build, test, and validation workflows with timing expectations
• Included critical timeout warnings to prevent premature cancellation of long-running operations

Comments suppressed due to low confidence (1)

.github/copilot-instructions.md:1

• The curl flags are inconsistent between the two dotnet installation commands. Line 13 uses -sSL while line 14 uses -fsSL. For consistency, both should use the same flags (recommend -fsSL as it includes fail-fast behavior).

# Purview Telemetry Source Generator

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