fix(newos4): regression test for checkpoint name round-trip (auto)

Task 3 of plan 2026-10-27_061724-newos4-checkpoint-name-mismatch.md.

New modules/test/test-vfs-checkpoint.js loads the real VirtualFileSystem and
SystemModule with guarded localStorage/indexedDB/window stubs and asserts:
 A1-A4 checkpoint('') returns the resolved name; two calls differ; the file
        exists under the returned name
 B1-B2 checkpoint-list shows the returned name; rollback(<that name>) is true
 C1-C4 the `checkpoint` command prints exactly the name it created (and an
        explicit name verbatim)

RED before the fix (v4.6.101):
  FAIL C2 printed name exists on disk — printed=2026-10-27T07:31:21.575Z
  listed=["2026-10-27T07:31:21.574Z"]
  test-vfs-checkpoint: 2 passed, 8 FAILED

GREEN after:
  $ node modules/test/test-vfs-checkpoint.js
  test-vfs-checkpoint: 10 passed, 0 failed

0 files changed, 0 insertions, 0 deletions