Add the extended Win32 prefix per filesystem operation and only when
the path reaches MAX_PATH, instead of rewriting the whole storage root.
Short paths keep their ordinary spelling, so listing, canonicalisation
and iteration semantics are unchanged.
Derive list() keys lexically from de-prefixed entries, and canonicalise
containment in the extended namespace but compare it in the ordinary one,
so prefixed and plain spellings are never mixed.
Keep the existing publication regression and cover drive/UNC spelling
plus long-key CRUD.
Signed-off-by: trvon <me@trevon.dev>
