Agent Skills: context-md-format

Authoring spec for CONTEXT.md and CONTEXT-MAP.md. Load this when you are about to write to or update a project's vocabulary glossary. Defines glossary-only scope, the single-vs-multi-context layout, opinionated naming rules, the file template, the lazy-create policy, and the inline-update discipline. Reader-side awareness (when to read CONTEXT.md, how to use canonical terms) lives in the shared baseline — see `shared/baseline/context-md-awareness.md`. This skill is the authoring counterpart, loaded only by agents with write authority.