Function detect_file_paths 

pub fn detect_file_paths(text: &str) -> Vec<FileSpec>

Auto-detect file paths from a unit description string.

Scans for patterns that look like source file paths (e.g., src/foo.rs, crates/bar/baz.ts). Supports optional mode suffixes:

• path.rs:tail:50 → Tail(50)
• path.rs:10-50 → Range(10, 50)

Deduplicates by path (first occurrence wins).