fix(release): reduce npm package size and harden smoke test

[simongdavies]

This pull request updates the build and release process for native addons and npm packaging, focusing on improving artifact handling, package size enforcement, and reliability of npm publish verification. The most significant changes streamline the build matrix for musl targets, enforce stricter packaging constraints, and simplify the binary build script.

Build and Packaging Improvements:

• The musl build steps in .github/workflows/publish.yml now explicitly build native addons in release mode with stripping enabled, and remove glibc artifacts to ensure only musl binaries are uploaded for that matrix leg.
• A new step enforces a maximum unpacked npm package size (300MB) and fails the workflow if exceeded, preventing accidental bloat.
• After running tests, a new step rebuilds native addons in release mode to ensure production artifacts are packaged.

NPM Publish Verification:

• The publish workflow's registry polling logic now checks both metadata and tarball availability (including shasum verification) before proceeding, improving reliability and removing a redundant separate tarball check step.

Build Script and Cross-Platform Artifacts:

• The scripts/build-binary.js script is simplified to only copy platform-specific .node files into the correct package subdirectories, rather than duplicating them in the main lib directory.
• The Justfile and package.json build scripts are updated to use the --strip flag for smaller, optimized native binaries in release builds.

[Copilot]

Pull request overview

Updates HyperAgent’s release/publish pipeline to produce smaller, release-optimized native artifacts and to make post-publish verification more reliable (including registry propagation + tarball availability checks).

Changes:

• Build native addons in release mode with stripping enabled (including explicit handling for musl-only artifact uploads).
• Add an npm package unpacked-size guard (300MB) during packing to prevent accidental bloat.
• Simplify the standalone binary build process to only place .node files in the appropriate package subdirectories, and harden the npm publish smoke-test polling to verify both metadata and tarball shasum.

Reviewed changes

Copilot reviewed 4 out of 4 changed files in this pull request and generated no comments.

File	Description
src/code-validator/guest/package.json	Builds the guest N-API addon in release mode with stripping to reduce artifact size.
scripts/build-binary.js	Stops duplicating .node files into the top-level lib/ directory; keeps them under the appropriate package directories for resolution.
Justfile	Ensures release builds of native addons use --strip (including Windows path) to reduce output size.
.github/workflows/publish.yml	Streamlines musl packaging, enforces max unpacked size, rebuilds release addons post-test, and strengthens smoke-test registry polling with tarball shasum verification.