Extend the Harness

1. Never hand-edit generated configs

.claude/settings.json and hooks/hooks.json generated. Edit skill-manifest.json, regenerate:

bash scripts/generate-hook-configs.sh --apply
bash scripts/generate-hook-configs.sh --check   # drift check (lefthook runs this pre-push)

2. Add a new rule (grep-expressible)

Per-edit checks live as sourceable libs under .claude/hooks/checks/ and run through the PostToolBatch dispatcher (post-tool-batch.sh) -- one process per parallel tool batch on Claude; Codex re-expands them to per-call wrappers via the generator.

0. First ask: can Biome/Ultracite express it? Single-element lint rules belong in the Biome config, not a hook (see the delegation header in checks/accessibility-check.lib.sh). Hooks are for cross-element, cross-file, workflow, or LLM-behavior rules.
1. Write checks/my-check.lib.sh exposing run_my_check() -- start from an existing *.lib.sh as template -- plus a thin .claude/hooks/my-check.sh wrapper (copy any 450-byte sibling).
2. Add the wrapper filename to the matcher block in skill-manifest.json (usually PostToolUse.Edit|Write).
3. Regenerate: bash scripts/generate-hook-configs.sh --apply.
4. Test: feed synthetic edit event on stdin: