Adds shares:listMembers, setMemberRole, removeMember, leave and preview,
and an optional removeMembers flag on shares:revoke. Redeeming a link
now records it on the membership (new optional shareLinkId plus index),
so disabling a link can remove exactly the people who joined through it.
All additive: clients that don't call the new functions behave as before.

Co-Authored-By: Claude Opus 5.5 <noreply@anthropic.com>