chore: ignore local AI tooling files

[dnlbox]

Summary

• ignore local agent tooling directories and state files
• keep AGENTS and BUILD_STATE style maintainer protocol out of public package history by default

Notes

• local AI tooling files were translated from the fhir-resource-diff practices but remain ignored and uncommitted
• no CHANGELOG entry because this is local maintainer tooling, not a user-facing package change

Verification

• pnpm lint
• pnpm typecheck
• pnpm test