Build the Zig core with the lockfile-pinned toolchain and package version, then launch the exact host executable CI produced on macOS and Linux. Assert that it starts successfully and reports the expected version; unit tests cover a stale binary and launch failure.
This is a non-publishing rehearsal. Local unit tests, a real rehearsal binary, typechecks, Pickier, and actionlint pass. No release, tag, or package was published.