NPM Explorer & Downloader troch lavril

Features:
- Search npm packages by name (configurable registry)
- View package version, description, and dependencies (collapsible tree)
- Navigate dependencies with Back button (session history)
- Download package tarball (dist.tarball)
- Download selected dependencies or download all recursively
- Recursive download shows progress (text + progress bar) and supports soft cancel
- Caching of package metadata via chrome.storage.local
- Dependency graph visualization (D3)