docs: add agent repository instructions

[gantoine]

Description
^{Explain the changes or enhancements you are proposing with this pull request.}

Adds a regular AGENTS.md file that directs agent-compatible tooling to the canonical repository instructions in CLAUDE.md.

Using a regular file keeps discovery working on checkouts configured with core.symlinks=false, while avoiding duplicated repository guidance.

Validation

• trunk fmt
• trunk check
• Confirmed AGENTS.md is a regular file, not a symlink
• git diff --cached --check

AI Assistance Disclosure

PostHog Code was used to inspect the change, run verification, create the branch and commits, address review feedback, and prepare this pull request. The canonical repository instructions remain maintained in CLAUDE.md.

Checklist
^{Please check all that apply.}

• I've tested the changes locally
• I've updated relevant comments
• I've assigned reviewers for this PR
• I've added unit tests that cover the changes

Screenshots (if applicable)

Not applicable.

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[greptile-apps]

Greptile Summary

This PR adds an agent-compatible alias for the existing repository guide. The main change is:

• Adds AGENTS.md as a symbolic link to CLAUDE.md.

Confidence Score: 4/5

The guide alias needs a portability fix before merging.

• Symlink-capable checkouts resolve the existing guide correctly.
• Checkouts with core.symlinks=false expose only the text CLAUDE.md, so agent tooling misses the instructions.

AGENTS.md

Important Files Changed

Filename	Overview
AGENTS.md	Adds a relative symlink to CLAUDE.md, with a portability issue on checkouts that materialize symlinks as plain files.

_{Reviews (1): Last reviewed commit: "docs: add agent repository guide alias" | Re-trigger Greptile}