Simplify: Code Review and Cleanup

Review all changed files for reuse, quality, and efficiency. Fix any issues found.

Phase 1: Determine the Diff Command

Determine the appropriate diff command (e.g. git diff, git diff --cached, git diff HEAD) based on the current git state. If the caller specifies which diff command to use, use that. Do NOT run the diff yourself — each review agent will run it independently to keep the diff out of the main agent's context.

If there are no git changes, review the most recently modified files that the user mentioned or that you edited earlier in this conversation.

Phase 2: Launch Four Review Agents in Parallel

Use the Agent tool to launch all four agents concurrently in a single message. Every Agent tool call must set model: "opus". Instruct each agent to run the diff command itself to obtain the diff.

Agent 1: Code Reuse Review

For each change:

1. Search for existing utilities and helpers that could replace newly written code. Look for similar patterns elsewhere in the codebase — common locations are utility directories, shared modules, and files adjacent to the changed ones.