up-3-modeling-domain-entities

Creates or updates the entity model (docs/entity_model.md) of a spec-driven project: a Mermaid erDiagram showing entities and relationships only, plus one attribute table per entity with business types, validation rules, lifecycle states and the words to avoid, so that it serves as the project's vocabulary. Checks that every noun used by requirements and use case specifications exists in the model and lists the use cases affected by a model change. Use when the user asks for an entity model, domain model, data model or glossary for a spec-driven or use-case-driven project, adds or changes an entity or attribute, says the specifications use two words for one thing or asks to fix the vocabulary, or when a specification uses a noun the model lacks. Not for draw.io drawings, database migrations or ORM code.