Review feedback: split the anchor/path and path/suffix on the structural
delimiter ":/" instead of a bare ":". Since the path and suffix always
start with "/", ":/" is the real delimiter, and a ":" *inside* a file or
directory name (which OpenCloud allows but MS Graph/OneDrive forbid) is
kept as part of the path instead of being mistaken for a separator.
A ":" sitting at a segment boundary (e.g. a name ending in ":") stays
ambiguous and must be percent-encoded as "%3A": the split works on the
literal ":/", so "%3A" is never a delimiter and decodes back to ":". This
is now documented in the code and the acceptance feature.
Tests: colon inside a name (with and without a suffix), the Stat path
carrying the colon, and the "%3A" boundary escape.
Cover the rewrite shapes the middleware handles end-to-end against a
real OpenCloud server: root-anchored, item-anchored, deep paths,
trailing colon, and the "/<path>:/<suffix>" sub-route form. Also
assert that NOT_FOUND and PERMISSION_DENIED both collapse to 404.
The /permissions sub-route is registered only at /v1beta1, and the
v1beta1 GetDriveItem handler is share-jail-only, so the v1beta1
mount of the middleware is exercised through the permissions
scenario, since there is no other v1beta1 endpoint that works for
regular personal-drive items.
