Constant MAX_SCANNED_DIRECTORIES 

const MAX_SCANNED_DIRECTORIES: usize = 500;

Collect qualifying files under one declared scan directory.

Sorted by path so the answer is stable between calls — directory iteration order is not. Symlinked directories are not followed: a link out of the working directory would silently widen what this reports beyond the project, and read_one still reads a symlinked file normally. Ceiling on directories entered during one scan.

The file cap alone does not bound a deep or wide tree that contains few matches — the walk still has to enter every directory to find that out.