fix(release): package Sharp native runtime

[chubes4]

Summary

• materialize only the target platform's locked Sharp native packages into release artifacts
• verify package URLs, versions, and SHA-512 integrity before extraction and reject unsupported targets early
• preserve both the runtime-playground dependency and aggregate npm package ownership so packed CLI consumers remain runnable

Supported targets

• Linux glibc: x64, arm64
• macOS: x64, arm64
• Windows: x64, arm64

Linux musl and other architectures remain outside the existing release target contract and fail explicitly.

Testing

• npm ci
• npm run build
• npm run test:sharp-release-runtime (7 passed)
• TMPDIR=/tmp npm run test:release-package-coverage
• actual npm pack tarball installed globally; wp-codebox --version and commands passed
• official WordPress ZIP and standalone CLI tarball execute with only Linux x64 Sharp packages
• git diff --check

Closes #2209