feat(pocket-base): add reusable keystone travel

README.md

@@ -51,6 +51,8 @@ After 250 Survival-mode block placements anywhere by default, the spawnable over
 
 Base IV owners can purchase and expand a persistent Pocket Base with `/basesettings pocket upgrade`. Activating a complete diamond-block portal frame inside the normal base with flint and steel opens one public entrance to the owner's grass platform in a private void world. Players and non-player living mobs can travel through the entrance and active return portal; items, projectiles, and vehicles are not transported. The owner can move the return portal by building and igniting another complete frame inside the unlocked Pocket Base boundary; only the newly activated return portal remains functional. Natural hostile and passive mob spawning is disabled by default. Owners can control each category independently with `/basesettings pocket mobs <hostile|passive> <enable|disable>`. An owner who wins a raid inside their own Pocket Base permanently unlocks owner-only Survival flight across the full build height and within the current Pocket Base boundary plus a 16-block warning buffer on every side. The owner can control that automatic privilege with `/basesettings pocket flight <enable|disable>`. After the raid unlock, the owner can ignite a complete gold-block portal frame inside the unlocked boundary; any player who passes through receives temporary flight within the same boundary and buffer until leaving the Pocket Base. The owner's automatic-flight preference does not affect portal-granted flight.
 
+Pocket Base owners can also craft a reusable **Pocket Base Keystone**. Its shaped recipe uses an Ender Pearl in the center, Netherite Ingots on the four cardinal slots, and Obsidian in the four corners. Right-clicking the keystone outside a Pocket Base instantly records the player's location and takes them to their own Pocket Base. Right-clicking it again inside their own Pocket Base returns them to that exact location when the world and destination remain available and safe. Saved returns survive reconnects and server restarts. A transferred keystone only works for a player who has unlocked their own Pocket Base.
+
 Owners can change biome metadata without altering Pocket Base blocks, entities, inventories, or portals by using `/basesettings pocket type <void|nether|overworld> <subtype>`. Void uses `the_void`; Nether and Overworld accept their compatible vanilla biome names, such as `crimson_forest` or `plains`. Each change defaults to 16 netherite blocks, is configurable, and affects applicable natural mob selection when spawning is enabled. The Pocket Base remains a void-generated normal-environment world; dimension-specific mechanics do not change.
 
 ## Administration