Stop presenting make runtime-bundle as a turnkey fresh-checkout bootstrap\nwhen the checked-in manifest is intentionally empty. The manifest comments,\nruntimebundle error messages, Make help, README, and AGENTS docs now all\ndescribe the same local-first flow: stage an archive, use a separate local\nmanifest copy with url/sha256, then bootstrap ./runtime from that manifest.\n\nKeep the existing package/fetch commands intact, and add a small runtimebundle\nregression test so the local-manifest guidance does not drift again.\n\nValidated with make help and GOCACHE=/tmp/banger-gocache go test\n./internal/runtimebundle.