Agent Skills: code-structure

S-phase skill for the codesmith implementation workflow. Produces the structural skeleton (the C-header-file analog) per Lock 7. For each plan identified in D-phase, generates the list of files to create/modify with purpose, type/interface/schema signatures, test file structure, and vertical-slice identification. Locks STRUCTURE not tactics — the actual TDD steps (test → impl → green → verify → commit) are P-phase's job. Spot-check user review; hands off to code-plan when structure is locked.