Use when designing or editing aggregates and their repositories in a FastAPI +
SQLAlchemy backend: files in `app/models/` and `app/repos/`. Triggers on edits
to those directories; on imports from `sqlalchemy.ext.asyncio`,
`sqlalchemy.orm`; on user mentions of "aggregate", "repository", "consistency
boundary", "ORM model with behavior", "use case loading". Encodes: SA model
with behavior (no separate domain layer by default), repos return SA models,
YAGNI on repo surface, typed `*Exception` raised from repo, no commit in repo,
one repo per aggregate root, named query methods over generic filter objects.
Do NOT use for: projects that have an explicit `domain/` directory wit…
