fix(ci): drop the darwin-x64 binary leg; track macos-latest for snapshots; restore size budget

- Build Binaries failed on macos-14/darwin-x64: onnxruntime (via the
  optional @huggingface/transformers) ships no darwin/x64 napi binding,
  so the compile step cannot resolve it. The Intel leg is gone.
- The snapshot workflow now runs on macos-latest instead of a pinned
  macos-26 — the newest GA image carries the newest CoreGlyphs bundles;
  anything newer than GA is the beta channel's job.
- The beta-channel commit pushed help.js and setup.js past the 400-line
  ceiling (CI caught it; my local gate ran before that commit):
  local-archive installs move to setup/local-archive.js with
  extractAndIndex injected, and the --beta help text tightened.