WR-01: Send only changed fields in profileMutation so admin-toggle-only
saves don't re-send displayName (blocking members with null displayName
from ever having their admin flag toggled).
WR-02: Revert the toggle to member!.isAdmin explicitly instead of
`member?.isAdmin ?? true` — the prior fallback was correct by coincidence
but semantically wrong for any error path where member is non-null.
WR-04: Remove member-derived field resets (displayName, isAdmin) from
handleClose — those belong to the useEffect sync that already tracks
member?.id/displayName/isAdmin. Only ephemeral fields (passwords, errors)
are reset on close, eliminating the stale-closure Cancel regression.
Co-Authored-By: Claude Sonnet 4.6 <noreply@anthropic.com>
