Function resolve_module_path 

pub fn resolve_module_path(
    root: &Path,
    module_name: &str,
    include_paths: &[String],
) -> Option<PathBuf>

Resolve a Perl module name to a workspace-relative filesystem path candidate.

The search order is:

1. Each include_path under root, rejecting path traversal.
2. Fallback to root/lib/<module>.pm.