Declare the scope of define expressions

Editor assessment

`docs` is the correct type for clarifying documentation, and the imperative verb `declare` keeps the subject spec-conformant, lowercase, and period-free. The phrasing is slightly inscrutable out of context — `the scope of define expressions` could momentarily be mistaken for a Conventional Commits scope change, when it actually means lexical scoping of `define` replacements. A scope such as `docs(config)` and a body quoting an example would make the entry self-explanatory in the log. None of this harms automation: docs commits are typically excluded from release notes, so no version-bump noise results. As written, it's a serviceable, spec-clean message that leans on the linked PR for the actual explanation.