Fix bugs in syncback process and enhance error handling

- Resolved issues with nested orphan file removal, ensuring that both top-level and nested orphan files are correctly handled.
- Improved directory removal logic to gracefully handle cases where directories may have already been removed, preventing crashes.
- Enhanced the path scanning algorithm to accurately collect all source directories defined in the project, addressing missing paths in the syncback process.
- Updated logging to provide clearer debug information during directory scanning and error handling in the syncback operations.

tests/rojo_test/roundtrip_util.rs

@@ -63,7 +63,8 @@ pub fn run_rojo_syncback_clean(project_path: &Path, input_path: &Path) -> bool {
 
     if !output.status.success() {
         eprintln!(
-            "rojo syncback failed:\nstdout: {}\nstderr: {}",
+            "rojo syncback failed (exit code {:?}):\nstdout: {}\nstderr: {}",
+            output.status.code(),
             String::from_utf8_lossy(&output.stdout),
             String::from_utf8_lossy(&output.stderr)
         );