feat: npm/cargo/go module collection

[Snider]

Summary

Collect package registry metadata and source for software preservation.

Use Case

Packages get unpublished (left-pad incident). Archive important packages.

Commands

# npm package
borg collect npm @monero-project/monero-ts

# Cargo crate
borg collect cargo monero-rs

# Go module
borg collect go github.com/monero-ecosystem/go-monero

Data Collected

• Package metadata (versions, deps, maintainers)
• Source tarballs for all versions
• README and docs

Output

packages/
├── npm/
│   └── @monero-project/
│       └── monero-ts/
│           ├── metadata.json
│           ├── 1.0.0.tgz
│           └── 1.1.0.tgz

Registries

Command	Registry
npm	registry.npmjs.org
cargo	crates.io
go	proxy.golang.org
pypi	pypi.org

Acceptance Criteria

• Fetch package metadata
• Download all version tarballs
• Support npm, cargo, go, pypi
• Create version index
• Handle scoped packages

[google-labs-jules]

Jules is on it. When finished, you will see another comment and be able to review a PR.

[google-labs-jules]

Ready for a review! A PR has been created.