feat(extract): build containment tree and traverse all containers

Add buildTree to mirror how TTS nests objects, with a display label
(Nickname or class Name). Generalize traverseMod to descend into any
object with ContainedObjects, not just bags, and add Nickname to
TTSObject.

packages/shared/src/types.ts

@@ -3,7 +3,10 @@
  * Mirrors the structure produced by BSON-deserializing a TTS save.
  */
 export interface TTSObject {
+  /** The object's class/type, e.g. `Card`, `Bag`, `Custom_Model`. */
   Name: string;
+  /** The display name; often empty in saves, so fall back to `Name`. */
+  Nickname?: string;
   GUID: string;
   Description: string;
   /** Set by `markParent` during traversal; not present in the raw save. */