housekeep-dead-code — Delete by category, then ratchet

Degree of freedom: MIXED. Category order, the --fix-type sequence, one-commit-per-category, and verification between commits [LOW freedom — run exactly]; whether a specific flagged item is truly dead [HIGH freedom].

Apply-now. plan-dead-code produced the reviewed keep/kill list and the baseline; this makes the repo match it and installs the gate that keeps it matched. Net dead code strictly ≤ before, and no behavior change.

This is the execution arm of plan-dead-code, the same way housekeep-gates executes audit-gate-logic and housekeep-design executes plan-uiux-unification.

Deletion is the approved execution of a plan. The plan-* preservation contract ("no removal without an approved proposal") is satisfied by that approval — not bypassed by this skill.