at-simplify

# Simplify `at-simplify → 4 cleanup agents in parallel → apply the fixes` You are improving the quality of the changed code, not hunting for bugs. Review it for reuse, simplification, efficiency, and altitude issues, then fix what you find. Do not look for correctness bugs — that is what `at-review` is for. ## Phase 0 — Gather the diff Run `git diff "@{upstream}...HEAD"` (or `git diff main...HEAD` / `git diff HEAD~1` if there's no upstream) to get the unified diff under review. If there are uncommitted changes, or the range diff is empty, also run `git diff HEAD` and include the working-tree changes in scope — the review often runs before the commit. If a PR number, branch name, or file path was passed as an argument, review that target instead. Treat this diff as the review scope. ## Phase 1 — Review (4 cleanup agents in parallel) Launch **4 independent review agents** using multi-agent capabilities, all in a single message so they run concurrently. Pass each agent the diff and one of the four angles below. Each returns its findings with `file`, `line`, a one-line `summary`, and the concrete cost (what is duplicated, wasted, or harder to maintain). ### Reuse Flag new code that re-implements something the codebase already has — Grep shared/utility modules and files adjacent to the change, and name the existing helper to call instead. ### Simplification Flag unnecessary complexity the diff adds: redundant or derivable state, copy-paste with slight variation, deep nes...