refactor: replace panics with proper error propagation

[duna-feline]

Changes

• Add UnsupportedFormat(String) error variant
• Replace unimplemented!() with Err(Error::UnsupportedFormat(...)) in file_utils.rs
• Replace .write().unwrap() with ? propagation
• Replace .unwrap_or_else(|| panic!(...)) with .ok_or_else(|| Error::...)? in path_utils.rs
• Replace .unwrap() in copy_object_file with proper error handling
• Fix panic-prone glob handling in llvm_utils.rs

Why

Library code should never panic. All error paths now return Result so callers can handle failures gracefully.