TDD plan for the gated G.3a core: a pure TeleportArrivalController state machine
(hold-until-hydration + force-snap on impossible/timeout) + its GameWindow wiring
(replace the unconditional arrival snap with recenter + deferred BeginArrival;
per-frame Tick; readiness predicate reusing the #107 login triplet) + the EnvCell
physics/visibility hydration decouple + the visual acceptance gate. G.3b/c/d get
their own plans after the gate.
Also syncs the spec: the readiness predicate reuses SampleTerrainZ + IsSpawnCellReady
+ IsSpawnClaimUnhydratable (the validated #107 login gate) rather than a new
IsLandblockApplied query — strictly more faithful, less new surface.
Co-Authored-By: Claude Opus 4.8 (1M context) <noreply@anthropic.com>
