The feat/download-root-rules merge added two tests asserting the joined
save_dir against a str(Path) expectation. `_calculate_relative_path` returns a
forward-slashed relative path that `os.path.join` appends to a native-spelled
root, so on Windows the value is "...\unet-archive\Flux.1 D/fantasy" while the
expectation is "...\unet-archive\Flux.1 D\fantasy" -- purely a separator
difference. Only those two assertions failed (3844 passed), and the Windows job
was green at the merge's first parent (b197793b).
Capture save_dir as a Path, like every other fake in this file, and compare
Path objects so the assertions pin the routed root -- their actual subject --
instead of the host separator.