The generator's whole body executed at module load, so any import of it
(test/gen-skill-docs.test.ts pulls assertSinglePreamble via require();
test/catalog-trim.test.ts imports helpers) regenerated all 71 SKILL.md
in place — the root cause of half the TREE_MUTATING serial-shard
entries (hazard class #2532). The body now lives in an exported
main(): number behind if (import.meta.main).
Semantics preserved exactly: failure exits are immediate (matching the
old top-level process.exit), success leaves the event loop to drain so
the llms.txt fire-and-forget IIFE finishes its write, and the module
stays synchronous/require()-able. Proofs: byte-identical --host all
output (git status clean), --dry-run stale-tree still exits 1 (the
skill-docs freshness lane depends on it), and the new
test/gen-skill-docs-import-purity.test.ts pins load-time purity via a
subprocess probe (mtime-based, so a dirty worktree can't false-fail).
Co-Authored-By: Claude Fable 5 <noreply@anthropic.com>
