ADR 0029: Use Pydantic from_attributes for UI API response schemas

Date: 2026-01-15

Context: UI API routers duplicated large amounts of manual field copying (getattr/list/dict fallbacks), increasing code size and creating inconsistent defaults across endpoints. Decision: Introduce a shared OrmOutModel base with model_config = ConfigDict(from_attributes=True) and move default/coercion logic (e.g. Enum->str, None->[]/{}, display fallbacks) into schema validators. Constraints: Avoid triggering SQLAlchemy lazy loads by validating only column-like attributes from ORM objects; build composite responses (e.g. commit detail metrics/artifacts) explicitly rather than relying on ORM relationships. Consequences: Routers can return ORM/dataclass objects directly, reducing boilerplate and centralizing response semantics in schemas; validation becomes more consistent and easier to evolve.