Inventory: per-player items backbone (DR-026 Phase 0)

Data-driven ItemDatabase catalog + per-player replicated InventorySlot ([GhostField] OwnerSendType.All, a StatModifier twin). Harvest reroutes to the firing player's personal inventory (optional ComponentLookup<GhostOwner> in ResourceHarvestSystem; remainder/un-owned -> ledger); the G-key InventoryDepositRequest RPC moves the bag into the shared ledger the build economy spends. Catalog asset (Aether/Ore/Biomass + Stone Pickaxe) wired into the Gameplay subscene; read-only HUD inventory panel. ushort ItemId subsumes ResourceId; byte Category/Tier baked for gear-tier progression. Session-only (no SaveData bump).

Play-validated host+client: catalog baked into both worlds, the re-baked player ghost carries InventorySlot with a clean handshake, a server write replicates to the client owner, the deposit RPC round-trips, and the HUD renders catalog names. See DR-026.

Co-Authored-By: Claude Opus 4.8 (1M context) <noreply@anthropic.com>

Assets/_Project/Scripts/Simulation/Items/ItemDatabase.cs

@@ -0,0 +1,17 @@
+using Unity.Entities;
+
+namespace ProjectM.Simulation
+{
+    /// <summary>
+    /// Singleton handle to the baked item-definition database (config, not replicated — baked identically
+    /// into both worlds from the gameplay subscene, exactly like <see cref="AbilityDatabase"/>). A distinct
+    /// component type, so <c>GetSingleton&lt;ItemDatabase&gt;()</c> resolves independently of the ability
+    /// database (singleton-ness is per type). Optional at runtime: consumers that read it use
+    /// <c>TryGetSingleton</c> and fall back to defaults (e.g. <c>Tuning.DefaultStackMax</c>) so the sim still
+    /// runs before the catalog is authored.
+    /// </summary>
+    public struct ItemDatabase : IComponentData
+    {
+        public BlobAssetReference<ItemDatabaseBlob> Value;
+    }
+}