Function build_default_walker 

pub fn build_default_walker(root: &Path) -> WalkBuilder

Build a multi-threaded WalkBuilder with sensible defaults.

• Respects .gitignore, .ignore, .git/exclude, and parent ignore files
• Does not follow symlinks
• Uses the ignore crate’s default thread pool

Callers that need to prune additional directories should use filter_entry with is_excluded_dir.