skill/scripts keeps command-metadata.json and the page JS; every .mjs entry
point, lib/, and live/ are gone (the binary owns those verbs). Adds the POSIX
launcher, impeccable.cmd, VERSION (copied from the new root ENGINE_VERSION),
scripts/fetch-engine.mjs (bun run fetch:engine) to pull the pinned binary
into skill/scripts/bin/<os>-<arch>/, and gitignores that bin dir.
Prepared with AI assistance (Claude Code).
