Add standalone dependency and environment manifests

[andrew]

Add parsers for smaller package and environment tools whose manifest and lock files contain direct or resolved dependency data.

• Pixi: add declarations from pixi.toml and [tool.pixi] in pyproject.toml, plus resolved Conda and PyPI packages from pixi.lock.
• Devbox: add package declarations from devbox.json and resolved packages from devbox.lock.
• Jsonnet Bundler: add declarations from jsonnetfile.json and pinned Git dependencies from jsonnetfile.lock.json.
• Mint: add Swift command-line package dependencies from Mintfile.
• Meteor: add declarations from package.js and resolved versions from .meteor/versions and versions.json.

Each completed checkbox should include parser registration, unit tests, fixtures, and README entries. Static parsing of package.js must not execute JavaScript or resolve dynamic expressions.