Replace the three monkeypatch-heavy tests from the salvaged commit (which
faked clear_legacy's return dict, so they could not catch the manager hunk
regressing) with two invariant tests that drive the real cmd_clear_legacy
against a temp checkpoint base: an undeletable legacy-* dir yields exit 2
plus the "Could not delete" line while the archive stays on disk; a clean
sweep keeps exit 0 and the unchanged success line. The green-path guard is
harvested from #111789.
Reword the CLI failure line to "Could not delete N archive(s) (see logs)."
so it matches the manager's WARNING wording and the text proposed in
#111776, and document the exit code in the CLI reference.
Co-authored-by: KoNit-K <124019182+KoNit-K@users.noreply.github.com>
Co-authored-by: Konstantin Khlopkov <47825603+kokhlo@users.noreply.github.com>
teknium1