Consolidate contribution guidance into CONTRIBUTING

[Goooler]

Summary

• merge repository development/contribution guidance from AGENTS.md into CONTRIBUTING.md
• keep AGENTS.md minimal and make it a strict pointer to CONTRIBUTING.md as the single source of truth
• update AGENTS.md wording in English and explicitly require strict compliance with CONTRIBUTING.md

Why

• avoid duplicated documentation and drift between two files
• keep contributor and automation guidance consistent in one canonical location

Notes for reviewers

• scope is docs-only (AGENTS.md, CONTRIBUTING.md)
• no runtime or build logic changes

[Copilot]

Pull request overview

This docs-only PR consolidates contributor and automation guidance into CONTRIBUTING.md and reduces AGENTS.md to a pointer to that canonical file.

Changes:

• Expands CONTRIBUTING.md with project overview, setup, build, style, CI, signing, and PR guidance.
• Replaces duplicated AGENTS.md guidance with a strict reference to CONTRIBUTING.md.

Reviewed changes

Copilot reviewed 2 out of 2 changed files in this pull request and generated 6 comments.

File	Description
CONTRIBUTING.md	Adds consolidated contribution and development guidance.
AGENTS.md	Replaces duplicated guidance with a minimal pointer to CONTRIBUTING.md.

---

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