Add code review instructions derived from PR feedback patterns

[SteveL-MSFT]

Copilot's automated code reviews sometimes flag false positives (e.g., claiming code won't compile when it does) or miss repo-specific patterns that human reviewers consistently catch. This PR adds a .github/instructions/code-review.instructions.md file to teach Copilot the recurring patterns and best practices specific to this repository.

Approach

Analyzed review comments across 30+ merged PRs spanning Dec 2025 -- Jul 2026, focusing on:

• Human reviewer feedback that corrected Copilot or identified issues Copilot missed
• Patterns where Copilot's feedback was accepted and led to fixes
• Recurring themes in maintainer comments

The resulting instructions file is organized by domain and covers:

• General principles -- avoid false compile-error claims, distinguish test harnesses from production code, recognize auto-generated files
• Rust patterns -- cache key correctness, API visibility, fail-closed security, Windows FFI/COM safety (DLL loading, Drop, HRESULT), what-if correctness, Option return types
• Pester test patterns -- cross-platform paths, env var isolation, ACL cleanup, exit code assertions, array comparisons, event subscriber cleanup, cmdlet skip guards
• PowerShell adapter patterns -- module array returns, $using: in parallel blocks, terminating vs non-terminating errors
• Design/architecture -- settings precedence chain, backward compatibility, semver conventions, canonical property naming, schema coherence
• CI/CD -- fork permission limitations, conditional tool installation
• Documentation -- debug print removal, locale string accuracy, dead i18n keys

Notes

• The applyTo frontmatter targets **/*.rs, **/*.ps1, **/*.psm1, **/*.tests.ps1, **/*.json to cover the main file types in this repo
• Instructions are phrased as actionable review guidance, not general coding advice
• The "General Principles" section specifically addresses known false-positive patterns to reduce noise in future reviews

[Copilot]

Pull request overview

This PR adds a repository-specific GitHub Copilot code review instruction set under .github/instructions/ to reduce recurring false positives and encode patterns maintainers commonly enforce across DSC’s Rust, PowerShell/Pester, and JSON changes.

Changes:

• Introduces a new Copilot code-review instruction file with guidance grouped by domain (Rust, PowerShell/Pester, architecture, CI/CD, docs/logging).
• Adds targeted “avoid noise” principles (e.g., CI-validated compile/test claims, test-harness vs production expectations, autogenerated file handling).

[github-actions]

Code Coverage Report

No Rust files were changed in this PR.

🔵 Full Codebase Coverage

81% (good)

Metric	Value
Total executable lines	18188
Lines covered by tests	14885
Coverage percentage	81%

Full codebase coverage measures all instrumented Rust lines across the project.

[Copilot]

Pull request overview

Copilot reviewed 1 out of 1 changed files in this pull request and generated no new comments.