The Windows CI runner failed the nested-git-repository arm, and the fault
was in the test's precondition assertion, not in the fix it was checking.

`os.tmpdir()` on that runner is `C:\Users\RUNNER~1\...` - an 8.3 short
name - while `resolveCanonicalProjectRoot` hands back the long spelling of
the same directory. The assertion compared the two directly, so it failed
on a path that named one place two ways.

Both sides now go through `realpathSync.native`, which resolves through
the OS handle and returns one canonical spelling. Measured on a host with
a real 8.3 name: the plain `realpathSync` leaves `A-VERY~1` unexpanded,
`realpathSync.native` expands it, and `native(short) === native(long)`.

The verdict assertions in the same file were already spelling-independent
- they read the action out of stdout - so only the path comparison moved.