docs: contributing guidelines and AI assistant instructions

[KSXGitHub]

Summary

This PR establishes comprehensive contributing guidelines and development standards for the project, along with quick-reference instructions for AI assistants.

Changes

• CONTRIBUTING.md: Complete contributor guide covering:
  • Conventional Commits format with type/scope/description rules
  • Code style conventions (import organization, module structure, derive macro ordering)
  • Generic parameter and trait bound guidelines
  • Visibility, error handling, and documentation standards
  • Feature gating and pattern matching conventions
  • Setup prerequisites and automated checks / CI validation procedures
• CLAUDE.md, AGENTS.md, .github/copilot-instructions.md: Identical quick-reference files for AI assistants (Claude Code, GitHub Copilot, Cursor, Codex) with key conventions from CONTRIBUTING.md
• tests/sync_ai_instructions.rs: Test to enforce the three AI instruction files stay in sync

Details

These documents establish clear expectations for:

• Commit message formatting using Conventional Commits
• Code organization (flat file pattern, import grouping, module structure)
• Type system practices (descriptive generics, where clauses, derive ordering)
• Error handling (custom error enums, minimize unwrap() in non-test code)
• Documentation requirements (doc comments, examples, backtick links)
• CI validation workflow (test.sh with multiple feature combinations)

https://claude.ai/code/session_0118JGKVwhgbK8NwHfrorHfx

[Copilot]

Pull request overview

Adds contributor and assistant-facing documentation to standardize development workflow, code style, and commit conventions for the parallel-disk-usage repository.

Changes:

• Introduces CONTRIBUTING.md with commit message conventions, Rust code style guidelines, and local/CI check instructions.
• Adds CLAUDE.md and .github/copilot-instructions.md to direct assistants to follow CONTRIBUTING.md, with a short quick-reference section.

Reviewed changes

Copilot reviewed 3 out of 3 changed files in this pull request and generated 6 comments.

File	Description
CONTRIBUTING.md	New contributor guide covering conventions and validation workflow.
CLAUDE.md	Claude-specific instructions pointing to CONTRIBUTING + quick reference.
.github/copilot-instructions.md	Copilot-specific instructions pointing to CONTRIBUTING + quick reference.

---

💡 Add Copilot custom instructions for smarter, more guided reviews. Learn how to get started.

You can also share your feedback on Copilot code review. Take the survey.

[github-actions]

Performance Regression Reports

commit: 075ab09

There are no regressions.

[Copilot]

Pull request overview

Adds contributor and AI-tooling guidance, and enforces that the repository’s AI instruction documents remain synchronized.

Changes:

• Introduces CONTRIBUTING.md documenting commit conventions, Rust style conventions, and local/CI check commands.
• Adds three AI instruction files (Claude, agents, Copilot) with a shared quick reference.
• Adds an integration test ensuring the AI instruction files stay in sync (excluding the title line).

Reviewed changes

Copilot reviewed 5 out of 5 changed files in this pull request and generated 5 comments.

Show a summary per file

File	Description
tests/sync_ai_instructions.rs	New test to compare instruction file bodies for exact sync.
CONTRIBUTING.md	New contributor guide codifying conventions and how to run checks.
CLAUDE.md	New Claude-specific instruction entrypoint pointing to CONTRIBUTING.md.
AGENTS.md	New generic AI agent instructions matching CLAUDE.md content.
.github/copilot-instructions.md	New Copilot instructions matching the other AI instruction files.

---

💡 Add Copilot custom instructions for smarter, more guided reviews. Learn how to get started.

You can also share your feedback on Copilot code review. Take the survey.

[Copilot]

Pull request overview

Adds contributor and AI-agent guidance documentation to the repo, plus a test to ensure the various AI instruction files remain identical over time.

Changes:

• Add CONTRIBUTING.md documenting commit conventions, Rust style conventions, and local/CI checks.
• Add synchronized AI instruction files (CLAUDE.md, AGENTS.md, .github/copilot-instructions.md) pointing contributors/agents to CONTRIBUTING.md.
• Add an integration test to verify the AI instruction files stay in sync.

Reviewed changes

Copilot reviewed 5 out of 5 changed files in this pull request and generated 4 comments.

Show a summary per file

File	Description
tests/sync_ai_instructions.rs	New test asserting the three AI instruction files are identical.
CONTRIBUTING.md	New contribution guidelines (commit format, style, checks).
CLAUDE.md	New AI instruction “quick reference” (intended to match the other instruction files).
AGENTS.md	Same AI instruction content as CLAUDE.md.
.github/copilot-instructions.md	Same AI instruction content as CLAUDE.md for Copilot.

---

💡 Add Copilot custom instructions for smarter, more guided reviews. Learn how to get started.

You can also share your feedback on Copilot code review. Take the survey.