This PR changes the shebang in `lean_profile.sh` from `#!/bin/bash` to
`#!/usr/bin/env bash` so the script works on NixOS and other systems
where bash is not at `/bin/bash`, and adds a Claude Code skill pointing
to the profiler documentation.
🤖 Prepared with Claude Code
Co-authored-by: Claude Opus 4.6 <noreply@anthropic.com>