fix: dont break when given paths that are files. filter on them instead.

[vic]

No description provided.

[Copilot]

Pull Request Overview

This PR updates the recursive file listing function to safely handle file paths (rather than only directories) and adds a corresponding test to ensure that passing a file path doesn’t break the import-tree logic.

• listFilesRecursive now checks for directories and returns files unchanged
• A new test case verifies behavior when given a file path instead of a directory

Reviewed Changes

Copilot reviewed 2 out of 2 changed files in this pull request and generated 2 comments.

File	Description
default.nix	Enhanced listFilesRecursive to detect directory vs. file inputs
checkmate.nix	Added test case for import-tree behavior when input is a file

Comments suppressed due to low confidence (1)

checkmate.nix:142

• This test invokes lit.leafs instead of the import-tree function, so it doesn’t actually exercise the new file-path branch. Consider calling the import-tree entrypoint to verify that passing a file path returns the correct singleton list.

          expr = lit.leafs ./tree/x/y.nix;