Added the system from trail

Runtime/EncounterRegistry.cs

@@ -0,0 +1,67 @@
+using System;
+using System.Collections.Generic;
+using UnityEngine;
+using UnityEngine.AddressableAssets;
+
+namespace Jovian.EncounterSystem {
+    /// <summary>
+    /// Central lookup cache mapping <see cref="EncounterDefinition.internalId"/> to its owning
+    /// <see cref="IEncounter"/> across one or more <see cref="EncountersCollection"/> assets.
+    /// In editor the registry auto-populates via an asset postprocessor; at runtime call
+    /// <see cref="PopulateEncounters"/> explicitly after load.
+    /// </summary>
+    [CreateAssetMenu(fileName = "EncounterRegistry", menuName = "Jovian/Encounter System/Encounter Registry")]
+    public class EncounterRegistry : ScriptableObject {
+        /// <summary>Collections whose encounters should be indexed.</summary>
+        public EncountersCollection[] encounterCollections = Array.Empty<EncountersCollection>();
+
+        private readonly Dictionary<string, IEncounter> encounters = new();
+
+        /// <summary>The live id → encounter map.</summary>
+        public Dictionary<string, IEncounter> GetEncounters() => encounters;
+
+        /// <summary>Add an encounter to the cache if its id isn't already present.</summary>
+        public void RegisterEncounter(IEncounter encounter) {
+            encounters?.TryAdd(encounter?.EncounterDefinition?.internalId, encounter);
+        }
+
+        /// <summary>Remove an encounter from the cache by its id.</summary>
+        public void UnregisterEncounter(IEncounter encounter) {
+            encounters.Remove(encounter.EncounterDefinition.internalId);
+        }
+
+        /// <summary>Clear the cache. Call before a full re-population to avoid stale entries.</summary>
+        public void ClearEncounters() {
+            encounters.Clear();
+        }
+
+        /// <summary>Walk <see cref="encounterCollections"/> and register every encounter found.
+        /// Call <see cref="ClearEncounters"/> first if you need a clean state.</summary>
+        public void PopulateEncounters() {
+            foreach(var collection in encounterCollections) {
+                foreach(var encounter in collection.encounterTables) {
+                    foreach(var encounterInstance in encounter.encounters) {
+                        RegisterEncounter(encounterInstance);
+                    }
+                }
+            }
+        }
+    }
+
+#if UNITY_EDITOR
+    /// <summary>
+    /// Editor-time hook that keeps an <see cref="EncounterRegistry"/> asset (located via Addressables
+    /// key <c>"EncounterRegistry"</c>) in sync with asset edits: clears and repopulates on any asset
+    /// import/move/delete.
+    /// </summary>
+    public class EncounterRegister : UnityEditor.AssetPostprocessor {
+        private static EncounterRegistry registryCache;
+
+        private static void OnPostprocessAllAssets(string[] importedAssets, string[] deletedAssets, string[] movedAssets, string[] movedFromAssetPaths) {
+            registryCache ??= Addressables.LoadAssetAsync<EncounterRegistry>("EncounterRegistry").WaitForCompletion();
+            registryCache.ClearEncounters();
+            registryCache.PopulateEncounters();
+        }
+    }
+#endif
+}