Agent Skills: ring:writing-trds

Writing a Technical Requirements Document that designs the technical architecture of the system or feature: components and boundaries, data flow, integration points, failure modes, and the mandatory program structure (DDD/hexagonal source tree) — in technology-agnostic patterns (code structure excepted), plus auth/pagination and BFF contracts for fullstack. Gate 3 of ring:planning-large-features (after ring:mapping-feature-relationships, before ring:designing-api-contracts) and Gate 2 of ring:planning-small-features (after ring:writing-prds, before ring:writing-plans). Use when the PRD passed validation. Skip when the PRD is unvalidated or the architecture is already documented.