product-capability

# Product Capability Turn accepted product intent into a local engineering contract. This Skill specifies one capability; it does not own implementation, ticketing, or delivery. Use `grill-me` first when consequential decisions remain. Use `grill-with-docs` when this work creates or changes a durable specification so the same decision graph is reconciled with repository evidence. ## Inputs Read only relevant sources: - accepted source facts from the user, current task, issues, PRDs, or roadmap notes - existing behavior, tests, schemas, interfaces, and durable docs - project instructions and ownership/security/rollout constraints Do not invent product truth. Label an inference or unresolved decision instead of smoothing over missing evidence. ## Specification Write the smallest artifact that makes implementation unambiguous: ```text CAPABILITY - actor, new behavior, and observable outcome ACCEPTED SOURCE FACTS - source anchor and fact CONSTRAINTS - invariants, ownership, trust, lifecycle, failure, migration, and rollout rules INTERFACES - inputs, outputs, states, errors, side effects, and compatibility boundaries TEST SEAMS - public behaviors and deterministic evidence that will prove acceptance OUT OF SCOPE - explicit non-goals and rejected expansion OPEN DECISIONS - unresolved choices that can still change implementation or acceptance HANDOFF - ready for implementation, needs alignment, or needs focused design review ``` Prefer updating the project's existin...