When element-tool source changes (pen-core/element-builders/, pen-mcp/
tools/, element-tool-defs*.ts, elements*.md), automatically regenerate
out/mcp-server.cjs so external MCP clients (Claude Code / Codex CLI /
Cursor) see the new tools.
Opt-in: requires \`git config core.hooksPath .githooks\` (one-time per
clone — same setup as the pre-commit version-sync hook). Without it,
the hook file sits dormant and dev rebuilds manually after element-tool
changes per add-checklist Step 8.
Real failure mode without this hook (2026-05-03): P3 shipped 94 v1
builders to source but mcp-server.cjs stayed 13 days stale; Codex CLI
+ gpt-5.5 generated 138 nodes, used 0 v1 tools.