Add Project Context & Workflow section to copilot-instructions.md

[Copilot]

Consolidates PRs #233, #234, #235: Adds repository ecosystem and development workflow documentation to GitHub Copilot instructions.

Changes

• New section positioned after title, before "Communication Guidelines"

  • Repository Ecosystem: Primary repo, design docs location, cetmodules dependency, CI/dev containers
  • Development Workflow: Fork-based model, PR upstreaming, quality standards

• Generic content: No hardcoded user forks—applicable to all developers

• Markdown compliance: MD012, MD022, MD032 (blank line spacing around headers/lists)

Provides Copilot with multi-repository development context and quality expectations.

Original prompt

Consolidate changes from PRs #233, #234, and #235 into a single PR.
Update .github/copilot-instructions.md to include a new section "Project Context & Workflow" after the main title and before "Communication Guidelines".
The content should be generic (avoiding hardcoded user forks) as follows:

Project Context & Workflow

Repository Ecosystem

• Primary Repository: Framework-R-D/phlex
• Design & Documentation: Framework-R-D/phlex-design (contains design docs, coding guidelines, etc.)
• Dependencies: Critical dependency on FNALssi/cetmodules for the build system.
• Container Images:
  • phlex-ci: Used by automated CI checks.
  • phlex-dev: Used for VSCode devcontainers and local development.

Development Workflow

• Model: Fork-based development. Developers should work on branches within their own forks.
• Upstreaming: Changes are upstreamed via Pull Requests (PRs) to the primary repository Framework-R-D/phlex.
• Quality Standards:
  • Adhere to design and coding guidelines in Framework-R-D/phlex-design.
  • Ensure code passes CI checks using the phlex-ci environment.
  • Minimize changes required for upstreaming.

Ensure correct Markdown formatting (blank lines around headers/lists).

This pull request was created from Copilot chat.

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[Copilot]

Pull request overview

This PR adds comprehensive repository ecosystem and development workflow documentation to the GitHub Copilot instructions, consolidating changes from three previous PRs (#233, #234, #235). The new section provides Copilot with essential context about the multi-repository development environment.

• Adds "Project Context & Workflow" section positioned strategically after the title
• Documents repository ecosystem including primary repo, design docs location, dependencies, and container images
• Describes fork-based development workflow and quality standards

[greenc-FNAL]

This PR is intended to provide more context to GitHub Copilot to improve the quality of its work on Phlex.