implement-spec-with-codex

# Implement Spec with Codex Run [implement-spec](../implement-spec/SKILL.md) exactly — same loop, same gates, same maintenance checkpoints — but Codex writes the code. Invoking this skill IS the explicit ask that authorizes `codex exec` delegation under the [codex](../codex/SKILL.md) skill. ## Role split - **Codex implements — whenever possible.** Default every implementation pass to a `codex exec`, sliced sharp and prompted per the codex skill (prompt blocks, sandbox choice, exec liveness). Run independent slices as concurrent execs in separate worktrees, exactly where implement-spec would fan out subagents. - **You orchestrate and review.** The spec loop stays yours: pick the next slice, reconcile plan with code, author each prompt end-to-end, integrate diffs, run the gates, review the merged tree, commit, update the handoff, run maintenance checkpoints. None of that delegates. Keep a pass yourself only when slicing it sharply would cost more than doing it — tiny fixups, plan reconciliation, integration conflicts. ## Rules - You own every result: read the full diff and run the verification yourself. "Codex says it's done" is never done. - Visual results carry implement-spec's two extra proofs (production-route pixel diff + unprimed critique) with double force here: a sandboxed Codex never saw its change render, so a pass that misses the production render path entirely arrives looking fully "verified". - A sandboxed Codex ships code it never saw r...