Add AGENTS.md symlink

[benthecarman]

Add AGENTS.md as a symlink to CLAUDE.md so Codex can load the same repository guidance.

[ldk-reviews-bot]

I've assigned @tankyleo as a reviewer!
I'll wait for their review and will help manage the review process.
Once they submit their review, I'll check if a second reviewer would be helpful.

[ldk-claude-review-bot]

This is a minimal PR — a single symlink file. The diff is:

• New file AGENTS.md (mode 120000, i.e., symlink) pointing to CLAUDE.md
• CLAUDE.md exists at the repo root, so the relative symlink target is valid

I've verified:

• The symlink target CLAUDE.md exists at the repo root
• The file mode 120000 is correct for a symlink
• The relative path is correct (both files in the same directory)
• No .gitattributes that could interfere with symlink handling
• No missing newline issue (symlink targets in git don't have trailing newlines)

No issues found.