feat: support AGENTS.md standard

[mykyta-kovalenko]

Description

Add AGENTS.md to support the AGENTS.md open standard for cross-platform AI coding agent compatibility. This allows tools like Codex, Cursor, Copilot, and Windsurf to understand repo conventions alongside Claude Code.

AGENTS.md contains platform-agnostic repo conventions (project overview, repository structure, skill format, writing guidelines, hooks, and commit format) derived from the existing CLAUDE.md. Both files currently carry full content because Claude Code does not yet natively read AGENTS.md (anthropics/claude-code#34235, anthropics/claude-code#6235). Once that lands, CLAUDE.md can be slimmed to Claude-specific extensions only.

Also fixes the missing very-good-analysis-upgrade skill entry in the repository structure trees (CLAUDE.md, AGENTS.md) and README skills table — it was added in #57 but these files were not updated.

Closes #49

Type of Change

• New feature (feat)

[claude]

Claude Code Review

This pull request is from a fork — automated review is disabled. A repository maintainer can comment @claude review to run a one-time review.

[RuiMiguel]

Looks good but now AGENTS.md and CLAUDE.md have the same content. It would be better to only have the content at AGENTS.md and just mention that file at CLAUDE.md

@AGENTS.md

Wdyt?

[ryzizub]

Looks good but now AGENTS.md and CLAUDE.md have the same content. It would be better to only have the content at AGENTS.md and just mention that file at CLAUDE.md

@AGENTS.md

Wdyt?

I think AGENTS.md actually can be just a symlink (for example check here https://github.com/manaflow-ai/cmux)

[RuiMiguel]

Looks good but now AGENTS.md and CLAUDE.md have the same content. It would be better to only have the content at AGENTS.md and just mention that file at CLAUDE.md

@AGENTS.md

Wdyt?

I think AGENTS.md actually can be just a symlink (for example check here https://github.com/manaflow-ai/cmux)

I don't think a symlink could be the best alternative. I was thinking into have all standard information at AGENTS, and CLAUDE will mention that file, but things like hooks, that are Claude specific, can be described at CLAUDE file instead of AGENTS. Maybe more topics in the future could be added, but right now is the one that came into my mind