Each ClaimLinkMember stores an owner player uid plus that player's
local claim index (resolved fresh at use, not trusted as stable) so
a claim link can reference existing vanilla claims without copying
their data. Buffer claim is intentionally not referenced here; it
resolves on demand via group ownership.
Adds a ClaimLink data model and ClaimLinkRegistry that loads from
and writes to the savegame's keyed data store (protobuf-net, via
WorldManager.SaveGame), so claim link state survives restarts
without touching vanilla claim data. Also silences nullable
warnings on statics that are guaranteed set by StartServerSide
before any use, and on TryGetValue out-params guarded by the if.
Table-drives dispatch for every vanilla /land subcommand (free,
info, list, adminfree, claim's new/grant/revoke/grow/shrink/etc.)
so each has a named hook to fill in.
Intercepts vanilla /land claim load|cancel to track a per-player
pending claim selection, and wires LandClaimAPI/Logger through
ModSystem so admin info can dump full claim state for debugging.
anth64