Function validate_context_files 

fn validate_context_files(bundle: &Bundle, issues: &mut Vec<ValidationIssue>)

Mirrors bundle_export.rs::export_bundle’s own context-file handling: each path must survive sanitize_context_relative_path (no absolute paths, no .. traversal, no drive letters), and no two entries may normalize to the same output path case-insensitively (the most common export/extract targets have case-insensitive filesystems).