Create comprehensive GitHub Copilot instructions with validated commands and timing specifications

[Copilot]

This PR creates a comprehensive .github/copilot-instructions.md file that provides GitHub Copilot coding agents with detailed guidance on how to work effectively in the IntelliPerf codebase. The instructions follow an imperative tone and include exhaustively validated commands with proper timeout specifications.

Key Features

Comprehensive Command Validation: Every command in the instructions has been tested and validated, with timing measurements documented:

• Python package installation: 90 seconds (tested)
• External dependencies: 45+ minutes with network timeout handling
• Code quality checks: <1 second (ruff commands validated)
• CI pipeline: 45+ minutes including GPU droplet provisioning

Critical Timeout Specifications: All long-running operations include explicit "NEVER CANCEL" warnings with specific timeout values:

• External tools installation: 60+ minutes timeout
• Pre-commit setup: 10+ minutes timeout
• IntelliPerf optimization runs: 45+ minutes timeout

Manual Validation Scenarios: Four complete end-to-end validation scenarios are defined:

1. Memory access pattern optimization and validation
2. Bank conflict detection and optimization
3. Atomic contention reduction validation
4. Multi-backend diagnose functionality (HIP, Triton, PyTorch)

Network Issue Handling: The instructions properly document expected network failures and provide workarounds:

• External dependency installation frequently fails due to PyPI timeouts
• Pre-commit hooks may fail to install due to network limitations
• Container usage recommended for reliable development environment

Development Workflow Support: Complete guidance for:

• Container-based development (Docker/Apptainer)
• Code quality enforcement (ruff linting/formatting)
• Testing approaches for GPU and non-GPU environments
• CI integration with AMD GPU hardware

The instructions start with a firm directive to "Always reference these instructions first and fallback to search or bash commands only when you encounter unexpected information that does not match the info here" as required.

This provides GitHub Copilot agents with the comprehensive guidance needed to work effectively in this complex GPU performance optimization codebase, with emphasis on proper timeout handling and validation procedures.

Fixes #138.

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