docs: add root AGENTS.md (agent-instruction coverage)

[OrionArchitekton]

Adds a root AGENTS.md so coding agents and external contributors get the repo's role, layout, contribution boundaries, and validation commands in one place. Both validation commands (ruff check ., pytest -q) were run successfully against this branch, and the file was checked against the CI leak gate's path pattern before commit.

🤖 Generated with Claude Code

Summary by CodeRabbit

• Documentation
  • Added comprehensive documentation defining repository responsibilities, operational boundaries, merge control policies, review processes, repository structure, ownership scope, security constraints, and validation procedures including code analysis and leak detection.

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[coderabbitai]

No actionable comments were generated in the recent review. 🎉

ℹ️ Recent review info

⚙️ Run configuration

Configuration used: Organization UI

Review profile: CHILL

Plan: Pro

Run ID: 4e0331ea-47e5-4f2f-83b0-5715e6f13eff

📥 Commits

Reviewing files that changed from the base of the PR and between 9e2ed8e and 19970f5.

📒 Files selected for processing (1)

• AGENTS.md

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📝 Walkthrough

Walkthrough

AGENTS.md documents the failclosed repository's operational model: merge admission control via a reviewer command seam, bot review-thread handling through GitHub GraphQL, repository layout, ownership boundaries, contribution safety constraints (no secrets or absolute paths in the mirror), and CI validation pipeline including ruff, pytest, and leak detection.

Changes

Repository operational documentation

Layer / File(s)	Summary
Repository role, boundaries, and validation AGENTS.md	AGENTS.md establishes failclosed as a merge admission control gate with reviewer command stdin/stdout contract, GitHub GraphQL bot interactions, scope boundaries, mirror sanitization constraints, and CI validation behavior (ruff + pytest + leak gate).

Estimated code review effort

🎯 1 (Trivial) | ⏱️ ~3 minutes

Poem

🐰 A gate to guard the merge, so tight,
With agent bounds defined just right,
No secrets leak, no paths astray,
The failclosed path charts the way.
Documentation sealed with care,
A rabbit's trust, beyond compare! 🛡️

🚥 Pre-merge checks | ✅ 5

✅ Passed checks (5 passed)

Check name	Status	Explanation
Description Check	✅ Passed	Check skipped - CodeRabbit’s high-level summary is enabled.
Title check	✅ Passed	The title clearly and specifically describes the main change: adding a root AGENTS.md file for agent instruction coverage, which matches the primary objective of the PR.
Docstring Coverage	✅ Passed	No functions found in the changed files to evaluate docstring coverage. Skipping docstring coverage check.
Linked Issues check	✅ Passed	Check skipped because no linked issues were found for this pull request.
Out of Scope Changes check	✅ Passed	Check skipped because no linked issues were found for this pull request.

_{✏️ Tip: You can configure your own custom pre-merge checks in the settings.}

✨ Finishing Touches

🧪 Generate unit tests (beta)

• Create PR with unit tests
• Commit unit tests in branch codex/agents-md-failclosed-20260612

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[gemini-code-assist]

Code Review

This pull request adds the AGENTS.md file, which documents the repository's role, layout, boundaries, starting points, and validation steps for the failclosed project. I have no feedback to provide as there are no review comments to assess.

Important

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