Agent Skills: shell-review

Use when reviewing or auditing a Bash / sh / zsh script (single file, PR diff, or whole scripts/ directory). Runs the 4-layer × 8-class methodology: syntax (bash -n), static (shellcheck + shfmt + custom regex sweeps), semantic (logic / secret / portability review), and runtime (dry-run / trace / bats). Outputs a structured findings report with severity-tagged blockers / logic_errors / suggestions.