Add AGENTS.md and a skills directory for AI coding agents

[jaladh-singhal]

Added shared instructions for AI coding agents (Claude Code, Codex, Cursor, etc.) working in this repo:

• AGENTS.md (repo root): project instructions that agents load at the start of every session. It covers the repo map, the dev and test loop, code conventions, and how to approach a change in this codebase.
  • Kept deliberately short (about 60 lines), since it uses context in every session. It points to docs/ rather than repeating them.
  • No CLAUDE.md: Claude Code reads AGENTS.md natively from v2.1.277, as long as no CLAUDE.md exists (claude --version to check).
• .agents/skills/: task-specific instructions that load only when a request matches a skill's description, or when it's run as a command (e.g. /skill-name), so they cost nothing until they're used.
  • Starts with pr-description as an example. It drafts a PR description in the team's usual format (Jira link, what/why, Testing with the dev build URL).
  • .agents/skills/ is the cross-tool location recommended by the Agent Skills spec. Claude Code only reads .claude/skills/, so that is a symlink to .agents/skills/ and one copy works for all tools.

Testing

• From the repo root, start a new Claude Code session and ask it something answered in AGENTS.md (e.g. "how do I run a single JS test?"). It should answer without searching the repo.
• On any feature branch, run /pr-description or just ask "write a PR description for this branch". Either should load the skill and produce a draft with the Jira link and the dev build URL.
• Please read through AGENTS.md and flag anything that doesn't match how you work, especially the Code conventions and "How to approach a change" sections.

[aventura121]

This is great, thanks for proposing it. One thing that may be helpful to explain in AGENTS.md, if you agree, is a note about the firefly_test_data dependency for the tests. Maybe something like, "Some Java and jest tests read data from a separate firefly_test_data repo, checked out next to this one (../firefly_test_data; internal, not on GitHub). If it's missing or out of date, those tests fail with file-not-found errors. That's a data gap, not a regression. FIREFLY_SKIP_TESTDATA=true skips the jest ones (src/firefly/jest.config.js)."