/digital-marketing-pro:four-core-documents — The Strategic Spine (61 Steps) This skill produces Part 3 of the engagement methodology: the four documents that together define the brand at strategic depth. Every channel strategy, every creative brief, every piece of copy reads back to these. Context efficiency Heavy skill. Grep before Read any referenced file, then only matched ranges with + . List before opening files. On re-invocation mid-session, skip files already in context. Specification: four-core-documents-spec.md — the exact 61 steps across the four documents. Engagement context: engag…