feat(spawn): configure per-world spawn areas

design/user-stories/us-003-configure-world-spawn-area.md

@@ -2,7 +2,7 @@
 type: User Story
 title: "US-003: Configure each world's spawn area"
 description: Let administrators define an independent center and circular safe-spawn radius for every world.
-status: backlog
+status: done
 ---
 
 # US-003: Configure each world's spawn area
@@ -11,17 +11,17 @@ As a **server administrator**, I want to configure the spawn area independently
 
 ## Acceptance criteria
 
-- [ ] Every world has an independent spawn center and maximum spawn distance.
-- [ ] Until an administrator sets a custom center, a world uses its native world spawn point.
-- [ ] `/spawnadmin set` stores the executing administrator's current world, coordinates, yaw, and pitch as that world's center and facing direction.
-- [ ] `/spawnadmin distance <blocks>` sets the current world's maximum spawn distance in blocks.
-- [ ] `/spawnadmin info` displays the current world's effective center, whether it is native or custom, and maximum distance.
-- [ ] The default maximum spawn distance is 20 blocks.
-- [ ] The spawn area is circular, and random horizontal points are sampled uniformly by area within its radius.
-- [ ] A maximum distance of `0` targets the configured center and adjusts it to the nearest safe block.
-- [ ] Negative, non-numeric, or otherwise invalid distances are rejected with an explanatory message.
-- [ ] Random destinations use the center's saved yaw and pitch.
-- [ ] Per-world centers and distances survive server and plugin restarts.
+- [x] Every world has an independent spawn center and maximum spawn distance.
+- [x] Until an administrator sets a custom center, a world uses its native world spawn point.
+- [x] `/spawnadmin set` stores the executing administrator's current world, coordinates, yaw, and pitch as that world's center and facing direction.
+- [x] `/spawnadmin distance <blocks>` sets the current world's maximum spawn distance in blocks.
+- [x] `/spawnadmin info` displays the current world's effective center, whether it is native or custom, and maximum distance.
+- [x] The default maximum spawn distance is 20 blocks.
+- [x] The spawn area is circular, and random horizontal points are sampled uniformly by area within its radius.
+- [x] A maximum distance of `0` targets the configured center and adjusts it to the nearest safe block.
+- [x] Negative, non-numeric, or otherwise invalid distances are rejected with an explanatory message.
+- [x] Random destinations use the center's saved yaw and pitch.
+- [x] Per-world centers and distances survive server and plugin restarts.
 
 ## Related