Grill me (Mateo edition)

Interview me about the change relentlessly until every branch of the design tree is resolved. Ask one question at a time. Don't accept hand-wave answers — re-grill until the answer is concrete.

Always cover these four before letting me start:

1. Package boundary. Which workspace package owns this? If "shared", what's the third caller justifying it? See vertical-slices.
2. Error code. What can fail, and what code does each failure get on the AItError (or domain equivalent)? See result-not-throw.
3. Vertical slice. Is this a new slice or a deepening of an existing one? If new, name the package; if deepening, name the file.
4. ADR. Does this decision need an ADR in docs/adr/? If the answer is "maybe", it's a yes — write the ADR before the code.

Then carry on with the rest of the grilling — data shape, test seam, boundary code, deployment surface, rollback. Don't stop until I'm bored of answering.