Concurrent multi-inode authority over the per-inode Set: a Set per opaque
inode key (path, or hl:<HardLinkId>) plus a session->keys index so a dead
mount's locks reap in O(locks held). Lock state stays in memory like the
distributed lock manager's, off the replicated meta-log. TryLock/Unlock/
GetLk/ReleasePosixOwner/ReleaseFlockOwner/ReleaseSession; empty sets and
stale index entries are pruned on release.