Automate prebuilt npm releases

[benvinegar]

Summary

• add the actual GitHub Actions release workflow for publishing prebuilt npm packages
• generalize prebuilt package staging from one host build to a multi-artifact release assembly flow
• add publish/retry helpers so platform packages publish before the top-level hunkdiff package

What this changes

This takes the prebuilt-binary work past the prototype stage from #12.

New release workflow

.github/workflows/release-prebuilt-npm.yml now:

• builds binaries on:
  • ubuntu-latest -> hunkdiff-linux-x64
  • macos-13 -> hunkdiff-darwin-x64
  • macos-14 -> hunkdiff-darwin-arm64
• uploads each platform binary as an artifact
• downloads all build artifacts into one staging job
• verifies that a tag like v0.3.0 matches package.json
• stages the publishable npm package directories from those artifacts
• verifies the staged tarballs
• dry-runs publish order in CI
• publishes to npm on tag pushes or manual workflow dispatch with publish=true

New scripts

• scripts/build-prebuilt-artifact.ts
  • packages the current host binary into an artifact directory for CI fan-in
• scripts/stage-prebuilt-npm.ts
  • now supports staging from dist/release/artifacts instead of only the local host build
• scripts/check-release-version.ts
  • ensures release tags match package.json
• scripts/publish-prebuilt-npm.ts
  • publishes staged platform packages first, then the top-level package
  • skips already-published versions so reruns can recover from partial publishes
• scripts/check-prebuilt-pack.ts
  • verifies all staged platform packages, not just the current host package

Packaging tweaks

• narrow the first actual published prebuilt matrix to:
  • hunkdiff-linux-x64
  • hunkdiff-darwin-x64
  • hunkdiff-darwin-arm64
• platform packages now publish only the binary payload; the top-level meta package owns the hunk bin entry

Validation

• bun run typecheck
• bun test
• bun run test:tty-smoke
• bun run check:pack
• bun run build:prebuilt:npm
• bun run check:prebuilt-pack
• bun run smoke:prebuilt-install
• bun run build:prebuilt:artifact
• bun run stage:prebuilt:release
• bun run check:prebuilt-pack
• bun run publish:prebuilt:npm -- --dry-run

Follow-up

Once this lands, the next real release can go through the prebuilt workflow instead of publishing the Bun-backed root package from the repo root.