(Feat) Add Build

.claude/CLAUDE.md

@@ -171,14 +171,28 @@ World objects (pickables, harvestables) are **not** NetworkObjects. They use the
 owns a synced set of inactive ids + server-side authority (health, loot, drops) via RPC.
 Add new harvestable/pickable-like world state here, not as per-object NetworkObjects.
 `ItemData` cannot cross the wire — map items to ids through `ItemDatabase`
-(**Tools ▸ Ashwild ▸ Rebuild Item Database** after adding items). `BuildRegistry` +
-`BuildableDatabase` mirror this for placed structures (which also accumulate to high counts).
+(**Tools ▸ Ashwild ▸ Rebuild Item Database** after adding items).
 
-This "no NetworkObjects" rule targets **high-count** world state (thousands of scatter objects,
-hundreds of builds) — making those NetworkObjects would flood the network. It is **not** absolute:
-a **transient, low-count** object that moves and needs smooth replication — the build ghost, one
-per player — is the case where a real **NetworkObject + client-authoritative NetworkTransform**
-is the better tool, and `BuildRegistry` spawns it as such. Pick by count and lifetime, not dogma.
+**Placed structures are the deliberate exception — they ARE NetworkObjects.** `BuildRegistry` spawns
+every committed build server-side (`ServerManager.Spawn`) and each one carries its own state on its
+own `BuiltStructure`. This used to be a data registry (a `SyncList` of pose records each client
+instantiated locally), and it was changed on purpose: the records never saved the GameObjects — those
+were instantiated locally anyway, so memory, colliders and draw calls were identical — they only saved
+FishNet's per-object bookkeeping, and they forced a **second, incompatible mechanism** for any build
+with real state (chests, cooking stations). One mechanism for walls, chests and campfires alike is
+worth the bookkeeping at co-op base scale. Buildables still cross the wire as ids through
+`BuildableDatabase`.
+
+This "no NetworkObjects" rule targets genuinely **high-count, stateless** world state — the thousands
+of scatter objects — where a per-object NetworkObject buys nothing. It is **not** a blanket ban, and
+two cases deliberately go the other way:
+
+- **Placed structures** (hundreds, and many of them stateful) — server-spawned NetworkObjects, see above.
+- **The build ghost** (transient, one per player, moves every frame) — a NetworkObject with a
+  client-authoritative NetworkTransform, spawned by `BuildRegistry`.
+
+Pick by **state and count together**, not by count alone: the moment an object needs its own
+replicated state, a data registry means hand-rolling what FishNet already does per object.
 
 ### Shared interactables (cooking stations, future chests/benches)